diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 6de72fe..ab4c3a8 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -11,6 +11,10 @@ variables:
   # Commit of ghc/ci-images repository from which to pull Docker images
   DOCKER_REV: 8d0224e6b2a08157649651e69302380b2bd24e11
 
+  # Sequential version number of all cached things.
+  # Bump to invalidate GitLab CI cache.
+  CACHE_REV: 0
+
 ############################################################
 # CI Step
 ############################################################
@@ -164,26 +168,40 @@ variables:
     - .test_ghcup_version
     - .darwin:aarch64
     - .root_cleanup
+  cache:
+    key: darwin-brew-$CACHE_REV
+    paths:
+      - .brew
+      - .brew_cache
+  before_script:
+    # Install brew locally in the project dir. Packages will also be installed here.
+    - git clone --depth=1 https://github.com/Homebrew/brew $CI_PROJECT_DIR/.brew
+    - export PATH="$CI_PROJECT_DIR/.brew/bin:$CI_PROJECT_DIR/.brew/sbin:$PATH"
+
+    # otherwise we seem to get intel binaries
+    - export HOMEBREW_CHANGE_ARCH_TO_ARM=1
+
+    # make sure to not pollute the machine with temp files etc
+    - mkdir -p $CI_PROJECT_DIR/.brew_cache
+    - export HOMEBREW_CACHE=$CI_PROJECT_DIR/.brew_cache
+    - mkdir -p $CI_PROJECT_DIR/.brew_logs
+    - export HOMEBREW_LOGS=$CI_PROJECT_DIR/.brew_logs
+    - mkdir -p $CI_PROJECT_DIR/.brew_tmp
+    - export HOMEBREW_TEMP=$CI_PROJECT_DIR/.brew_tmp
+
+    # update and install packages
+    - brew update
+    - brew install llvm
+    - brew install autoconf automake coreutils
   script: |
-    set -Eeuo pipefail
-    function runInNixShell() {
-      time nix-shell $CI_PROJECT_DIR/.gitlab/shell.nix \
-        -I nixpkgs=https://github.com/angerman/nixpkgs/archive/75f7281738b.tar.gz \
-        --argstr system "aarch64-darwin" \
-        --pure \
-        --keep CI_PROJECT_DIR \
-        --keep MACOSX_DEPLOYMENT_TARGET \
-        --keep JSON_VERSION \
-        --keep ARTIFACT \
-        --keep OS \
-        --keep ARCH \
-        --keep CABAL_DIR \
-        --keep GHC_VERSION \
-        --keep CABAL_VERSION \
-        --run "$1" 2>&1
-    }
-    runInNixShell ./.gitlab/before_script/darwin/install_deps.sh 2>&1
-    runInNixShell ./.gitlab/script/ghcup_version.sh 2>&1
+    export PATH="$CI_PROJECT_DIR/.brew/opt/llvm/bin:$CI_PROJECT_DIR/.brew/bin:$CI_PROJECT_DIR/.brew/sbin:$PATH"
+    export CC=$CI_PROJECT_DIR/.brew/opt/llvm/bin/clang
+    export CXX=$CI_PROJECT_DIR/.brew/opt/llvm/bin/clang++
+    export LD=ld
+    export AR=$CI_PROJECT_DIR/.brew/opt/llvm/bin/llvm-ar
+    export RANLIB=$CI_PROJECT_DIR/.brew/opt/llvm/bin/llvm-ranlib
+    ./.gitlab/before_script/darwin/install_deps.sh
+    ./.gitlab/script/ghcup_version.sh
 
 .test_ghcup_version:freebsd12:
   extends:
@@ -508,26 +526,40 @@ release:darwin:aarch64:
     - .darwin:aarch64
     - .release_ghcup
     - .root_cleanup
+  cache:
+    key: darwin-brew-$CACHE_REV
+    paths:
+      - .brew
+      - .brew_cache
+  before_script:
+    # Install brew locally in the project dir. Packages will also be installed here.
+    - git clone --depth=1 https://github.com/Homebrew/brew $CI_PROJECT_DIR/.brew
+    - export PATH="$CI_PROJECT_DIR/.brew/bin:$CI_PROJECT_DIR/.brew/sbin:$PATH"
+
+    # otherwise we seem to get intel binaries
+    - export HOMEBREW_CHANGE_ARCH_TO_ARM=1
+
+    # make sure to not pollute the machine with temp files etc
+    - mkdir -p $CI_PROJECT_DIR/.brew_cache
+    - export HOMEBREW_CACHE=$CI_PROJECT_DIR/.brew_cache
+    - mkdir -p $CI_PROJECT_DIR/.brew_logs
+    - export HOMEBREW_LOGS=$CI_PROJECT_DIR/.brew_logs
+    - mkdir -p $CI_PROJECT_DIR/.brew_tmp
+    - export HOMEBREW_TEMP=$CI_PROJECT_DIR/.brew_tmp
+
+    # update and install packages
+    - brew update
+    - brew install llvm
+    - brew install autoconf automake
   script: |
-    set -Eeuo pipefail
-    function runInNixShell() {
-      time nix-shell $CI_PROJECT_DIR/.gitlab/shell.nix \
-        -I nixpkgs=https://github.com/angerman/nixpkgs/archive/75f7281738b.tar.gz \
-        --argstr system "aarch64-darwin" \
-        --pure \
-        --keep CI_PROJECT_DIR \
-        --keep MACOSX_DEPLOYMENT_TARGET \
-        --keep JSON_VERSION \
-        --keep ARTIFACT \
-        --keep OS \
-        --keep ARCH \
-        --keep CABAL_DIR \
-        --keep GHC_VERSION \
-        --keep CABAL_VERSION \
-        --run "$1" 2>&1
-    }
-    runInNixShell ./.gitlab/before_script/darwin/install_deps.sh 2>&1
-    runInNixShell ./.gitlab/script/ghcup_release.sh 2>&1
+    export PATH="$CI_PROJECT_DIR/.brew/opt/llvm/bin:$CI_PROJECT_DIR/.brew/bin:$CI_PROJECT_DIR/.brew/sbin:$PATH"
+    export CC=$CI_PROJECT_DIR/.brew/opt/llvm/bin/clang
+    export CXX=$CI_PROJECT_DIR/.brew/opt/llvm/bin/clang++
+    export LD=ld
+    export AR=$CI_PROJECT_DIR/.brew/opt/llvm/bin/llvm-ar
+    export RANLIB=$CI_PROJECT_DIR/.brew/opt/llvm/bin/llvm-ranlib
+    ./.gitlab/before_script/darwin/install_deps.sh
+    ./.gitlab/script/ghcup_release.sh
   variables:
     ARTIFACT: "aarch64-apple-darwin-ghcup"
     GHC_VERSION: "8.10.7"
diff --git a/.gitlab/ghcup_env b/.gitlab/ghcup_env
index 0b807ca..7a8ecd9 100644
--- a/.gitlab/ghcup_env
+++ b/.gitlab/ghcup_env
@@ -6,6 +6,6 @@ if [ "${OS}" = "WINDOWS" ] ; then
 else
 	export GHCUP_INSTALL_BASE_PREFIX="$CI_PROJECT_DIR"
 	export GHCUP_BIN="$CI_PROJECT_DIR/.ghcup/bin"
-	export PATH="$GHCUP_BIN:$CI_PROJECT_DIR/.local/bin:/opt/llvm/bin:$PATH"
+	export PATH="$GHCUP_BIN:$CI_PROJECT_DIR/.local/bin:$PATH"
 	export TMPDIR="$CI_PROJECT_DIR/tmp"
 fi
diff --git a/.gitlab/shell.nix b/.gitlab/shell.nix
deleted file mode 100644
index 33c7c67..0000000
--- a/.gitlab/shell.nix
+++ /dev/null
@@ -1,90 +0,0 @@
-{ system ? "aarch64-darwin"
-#, nixpkgs ? fetchTarball https://github.com/angerman/nixpkgs/archive/257cb120334.tar.gz #apple-silicon.tar.gz
-, pkgs ? import <nixpkgs> { inherit system; }
-, compiler ? if system == "aarch64-darwin" then "ghc8103Binary" else "ghc8103"
-}: pkgs.mkShell {
-  # this prevents nix from trying to write the env-vars file.
-  # we can't really, as NIX_BUILD_TOP/env-vars is not set.
-  noDumpEnvVars=1;
-
-  # stop polluting LDFLAGS with -liconv
-  dontAddExtraLibs = true;
-
-  # we need to inject ncurses into --with-curses-libraries.
-  # the real fix is to teach terminfo to use libcurses on macOS.
-  # CONFIGURE_ARGS = "--with-intree-gmp --with-curses-libraries=${pkgs.ncurses.out}/lib";
-  CONFIGURE_ARGS = "--with-intree-gmp --with-curses-libraries=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib --with-iconv-includes=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include --with-iconv-libraries=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib SH=/bin/bash";
-
-  # magic speedup pony :facepalm:
-  #
-  # nix has the ugly habbit of duplicating ld flags more than necessary.  This
-  # somewhat consolidates this.
-  shellHook = ''
-  export NIX_LDFLAGS=$(for a in $NIX_LDFLAGS; do echo $a; done |sort|uniq|xargs)
-  export NIX_LDFLAGS_FOR_TARGET=$(for a in $NIX_LDFLAGS_FOR_TARGET; do echo $a; done |sort|uniq|xargs)
-  export NIX_LDFLAGS_FOR_TARGET=$(comm -3 <(for l in $NIX_LDFLAGS_FOR_TARGET; do echo $l; done) <(for l in $NIX_LDFLAGS; do echo $l; done))
-
-
-  # Impurity hack for GHC releases.
-  #################################
-  # We don't want binary releases to depend on nix, thus we'll need to make sure we don't leak in references.
-  # GHC externally depends only on iconv and curses.  However we can't force a specific curses library for
-  # the terminfo package, as such we'll need to make sure we only look in the system path for the curses library
-  # and not pick up the tinfo from the nix provided ncurses package.
-  #
-  # We also need to force us to use the systems COREFOUNDATION, not the one that nix builds. Again this is impure,
-  # but it will allow us to have proper binary distributions.
-  #
-  # do not use nixpkgs provided core foundation
-  export NIX_COREFOUNDATION_RPATH=/System/Library/Frameworks
-  # drop curses from the LDFLAGS, we really want the system ones, not the nix ones.
-  export NIX_LDFLAGS=$(for lib in $NIX_LDFLAGS; do case "$lib" in *curses*);; *) echo -n "$lib ";; esac; done;)
-  export NIX_CFLAGS_COMPILE+=" -Wno-nullability-completeness -Wno-availability -Wno-expansion-to-defined -Wno-builtin-requires-header -Wno-unused-command-line-argument"
-
-  # unconditionally add the MacOSX.sdk and TargetConditional.h
-  export NIX_CFLAGS_COMPILE+=" -isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include"
-  export NIX_LDFLAGS="-L/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib $NIX_LDFLAGS"
-
-  '';
-
-  nativeBuildInputs = (with pkgs; [
-    # This needs to come *before* ghc,
-    # otherwise we migth end up with the clang from
-    # the bootstrap GHC in PATH with higher priority.
-    clang_11
-    llvm_11
-
-    haskell.compiler.${compiler}
-    haskell.packages.${compiler}.cabal-install
-    haskell.packages.${compiler}.alex
-    haskell.packages.${compiler}.happy # _1_19_12 is needed for older GHCs.
-
-    automake
-    autoconf
-    m4
-
-    gmp
-    zlib.out
-    zlib.dev
-    glibcLocales
-    # locale doesn't build yet :-/
-    # locale
-
-    git
-
-    python3
-    # python3Full
-    # python3Packages.sphinx
-    perl
-
-    which
-    wget
-	curl
-    file
-
-    xz
-    xlibs.lndir
-
-    cacert ])
-  ++ (with pkgs.darwin.apple_sdk.frameworks; [ Foundation Security ]);
-}