remove unused -MMD handling in the configure

Author: omar-polo

configure.ac

@@ -36,19 +36,6 @@ AC_CHECK_HEADER([sys/tree.h], [], [
 	CFLAGS="$CFLAGS -I$srcdir/openbsd-compat/tree"
 ])
 
-AC_DEFUN([CC_ADD_CHECK_FLAGS], [
-	AC_MSG_CHECKING([if $CC supports $1 flag])
-	old_CFLAGS="$CFLAGS"
-	CFLAGS="$CFLAGS $1"
-	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])], [
-		AC_MSG_RESULT(yes)
-	], [
-		AC_MSG_RESULT(no)
-		CFLAGS="$old_CFLAGS"
-	])
-])
-CC_ADD_CHECK_FLAGS([-MMD])
-
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_FILES([
 	Makefile