build: Use default compiler flags

acinclude.m4

@@ -0,0 +1,26 @@
+AC_DEFUN([AC_PROG_CC_PIE], [
+	AC_CACHE_CHECK([whether ${CC-cc} accepts -fPIE], ac_cv_prog_cc_pie, [
+		echo 'void f(){}' > conftest.c
+		if test -z "`${CC-cc} -fPIE -pie -c conftest.c 2>&1`"; then
+			ac_cv_prog_cc_pie=yes
+		else
+			ac_cv_prog_cc_pie=no
+		fi
+		rm -rf conftest*
+	])
+])
+
+AC_DEFUN([COMPILER_FLAGS], [
+	if (test "${CFLAGS}" = ""); then
+		CFLAGS="-Wall -O2 -D_FORTIFY_SOURCE=2 -fsigned-char"
+	fi
+	if (test "$USE_MAINTAINER_MODE" = "yes"); then
+		CFLAGS+=" -Werror -Wextra"
+		CFLAGS+=" -Wno-unused-parameter"
+		CFLAGS+=" -Wno-missing-field-initializers"
+		CFLAGS+=" -Wdeclaration-after-statement"
+		CFLAGS+=" -Wmissing-declarations"
+		CFLAGS+=" -Wredundant-decls"
+		CFLAGS+=" -Wcast-align"
+	fi
+])

configure.ac

@@ -14,7 +14,12 @@ AM_MAINTAINER_MODE
 
 AC_PREFIX_DEFAULT(/usr/local)
 
+COMPILER_FLAGS
+
+AC_LANG_C
+
 AC_PROG_CC
+AC_PROG_CC_PIE
 AC_PROG_INSTALL
 AC_PROG_MKDIR_P
 AC_PROG_LN_S