fix: makefile builds with mingw

.github/workflows/test.yml

@@ -212,3 +212,34 @@ jobs:
       - name: CTest
         shell: msys2 {0}
         run: ctest --no-tests=error --test-dir out -VV --build-config Release
+
+  msys2-makefile-test:
+    name: msys2-makefile-${{ matrix.msystem }}
+    needs: makefile-analysis
+    runs-on: windows-2022
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { msystem: msys, toolchain: "gcc" }
+          # - { msystem: mingw32, env: mingw-w64-i686- }  disabled, c.f. https://github.com/aklomp/base64/issues/131
+          - { msystem: mingw64, env: mingw-w64-x86_64- }
+          - { msystem: ucrt64, env: mingw-w64-ucrt-x86_64- }
+          - { msystem: clang32, env: mingw-w64-clang-i686- }
+          - { msystem: clang64, env: mingw-w64-clang-x86_64- }
+    env:
+      CC: cc.exe
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Setup MSYS2 ${{matrix.msystem}}
+        uses: msys2/setup-msys2@v2
+        with:
+          msystem: ${{matrix.msystem}}
+          update: true
+          install: >-
+            make
+            ${{ matrix.env }}${{ matrix.toolchain || 'toolchain' }}
+      - name: Run tests
+        shell: msys2 {0}
+        run: ./test/ci/test.sh

Makefile

@@ -1,4 +1,4 @@
-CFLAGS += -std=c99 -O3 -Wall -Wextra -pedantic
+CFLAGS += -std=c99 -O3 -Wall -Wextra -pedantic -DBASE64_STATIC_DEFINE
 
 # Set OBJCOPY if not defined by environment:
 OBJCOPY ?= objcopy