Make: Support CFLAGS as both env var and make argument

We usually pass arguments to make through environment variables:
CFLAGS="-std=c11" make quickcheck

It currently does not work to pass it as a make argument:
make quickcheck CFLAGS="-std=c11"

This commit fixes that and extends the C90 CI to test both variants.

Resolves #722

Signed-off-by: Matthias J. Kannwischer <[email protected]>

Author: mkannwischer

.github/workflows/base.yml

@@ -153,11 +153,17 @@ jobs:
     runs-on: ${{ matrix.target.runner }}
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
-      - name: make quickcheck
+      - name: make quickcheck (CFLAGS as environment variable)
+        run: |
+          OPT=0 CFLAGS="-std=c90" make quickcheck
+          make clean >/dev/null
+          OPT=1 CFLAGS="-std=c90" make quickcheck
+      - name: make quickcheck (CFLAGS as make argument)
         run: |
-          OPT=0 CFLAGS=-std=c90 make quickcheck
           make clean >/dev/null
-          OPT=1 CFLAGS=-std=c90 make quickcheck
+          OPT=0 make quickcheck CFLAGS="-std=c90"
+          make clean >/dev/null
+          OPT=1 make quickcheck CFLAGS="-std=c90"
       - uses: ./.github/actions/setup-apt
       - name: tests func
         run: |

test/mk/config.mk

@@ -31,7 +31,8 @@ CC_AR  := $(CROSS_PREFIX)$(CC_AR)
 #################
 # Common config #
 #################
-CFLAGS := \
+
+override CFLAGS := \
 	-Wall \
 	-Wextra \
 	-Werror=unused-result \