Restructure Makefiles

Use common.mk for basic toolchain settings and installation variables.

common.mk

@@ -0,0 +1,24 @@
+# compiler, tools
+CC = clang
+PKG_CONFIG ?= pkg-config
+
+# flags
+CFLAGS ?= -march=native -O2 -pipe
+CFLAGS += -std=c99 -pedantic -Wall -Wextra -Werror -Wno-unused-variable -Wno-unused-parameter -Wno-unused-function
+ifeq ($(shell $(CC) -v 2>&1 | grep 'gcc version' &>/dev/null && echo 1),1)
+CFLAGS += -Wno-unused-but-set-variable
+endif
+LDFLAGS ?= -Wl,-O1 -Wl,--as-needed -Wl,--hash-style=gnu
+
+ifndef NODEBUG
+CFLAGS += -O0 -g3
+endif
+
+# install variables
+INSTALL = install
+INSTALL_BIN = install -m755
+INSTALL_DIR = install -d
+PREFIX = /usr/local
+LIBDIR = lib64
+INSTALL_BINDIR = $(PREFIX)/bin
+INSTALL_LIBDIR = $(PREFIX)/$(LIBDIR)