configure: now you can do multiple compilers!

configure

@@ -14,13 +14,15 @@ RUSTFLAGS='-Copt-level=z -Ccodegen-units=1 -Cpanic=abort -Clto=y \
 	-Cstrip=symbols -Ctarget-cpu=native \
 	--extern sysexits=build/o/libsysexits.rlib'
 
-case "$@" in
-	clang)
-		CFLAGS="$CFLAGS -Wall"
-		;;
-	clean)
+if [ "$1" = "clean" ]; then
 	rm *.mk || true
 	exit 0
+fi
+
+while test -n "$1"; do
+	case "$1" in
+		clang)
+			CFLAGS="$CFLAGS -Wall"
 			;;
 		gcc)
 			CFLAGS="$CFLAGS -s -Wl,-z,noseparate-code,-z,nosectionheader -flto"
@@ -28,12 +30,14 @@ case "$@" in
 		'rustc +nightly')
 			RUSTFLAGS="+nightly -Zlocation-detail=none $RUSTFLAGS"
 			;;
-	'') ;;
 		*)
-		printf 'Usage: %s [compiler]\n' "$0"
+			printf 'Usage: %s [clean | compiler]\n' "$0"
 			exit 64 # sysexits.h(3) EX_USAGE
 			;;
-esac
+	esac
+
+	shift
+done
 
 printf 'CFLAGS=%s\n' "$CFLAGS" >cc.mk
 printf 'RUSTFLAGS=%s\n' "$RUSTFLAGS" >rustc.mk