Re-introduce tar

ghcup.cabal

@@ -53,6 +53,11 @@ flag no-exe
   default:     False
   manual:      True
 
+flag tar
+  description: Use haskell tar instead of libarchive.
+  default:     False
+  manual:      True
+
 common app-common-depends
   build-depends:
     , aeson                  >=1.4
@@ -68,7 +73,6 @@ common app-common-depends
     , filepath               ^>=1.4.2.1
     , haskus-utils-types     ^>=1.5
     , haskus-utils-variant   ^>=3.2.1
-    , libarchive             ^>=3.0.3.0
     , megaparsec             >=8.0.0    && <9.3
     , mtl                    ^>=2.2
     , optparse-applicative   >=0.15.1.0 && <0.18
@@ -90,6 +94,15 @@ common app-common-depends
     , versions               >=6.0.3    && <6.1
     , yaml-streamly          ^>=0.12.0
 
+  if flag(tar)
+    cpp-options:   -DTAR
+    build-depends:
+        tar ^>=0.6.0.0
+      , zip ^>=2.0.0
+
+  else
+    build-depends: libarchive ^>=3.0.3.0
+
 library
   exposed-modules:
     GHCup
@@ -166,7 +179,6 @@ library
     , filepath              ^>=1.4.2.1
     , haskus-utils-types    ^>=1.5
     , haskus-utils-variant  ^>=3.2.1
-    , libarchive            ^>=3.0.3.0
     , lzma-static           ^>=5.2.5.3
     , megaparsec            >=8.0.0      && <9.3
     , mtl                   ^>=2.2
@@ -196,6 +208,15 @@ library
     , yaml-streamly         ^>=0.12.0
     , zlib                  ^>=0.6.2.2
 
+  if flag(tar)
+    cpp-options:   -DTAR
+    build-depends:
+        tar ^>=0.6.0.0
+      , zip ^>=2.0.0
+
+  else
+    build-depends: libarchive ^>=3.0.3.0
+
   if (flag(internal-downloader) && !os(windows))
     exposed-modules: GHCup.Download.IOStreams
     cpp-options:     -DINTERNAL_DOWNLOADER