CI: test all compilers on all OSes

.github/workflows/d.yml

@@ -15,20 +15,42 @@ permissions:
 
 jobs:
   build:
-
-    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        dc: [dmd, ldc]
+        include:
+          - { os: ubuntu-latest, dc: gdc-14 }
+    runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v3
-    - uses: dlang-community/setup-dlang@4c99aa991ce7d19dd3064de0a4f2f6b2f152e2d7
+      - uses: actions/checkout@v4
+      - uses: dlang-community/setup-dlang@v2
+        with:
+          compiler: ${{ matrix.dc }}
+          dub: latest
+
+      - name: Setup gdc specific environment
+        if: ${{ startsWith(matrix.dc, 'gdc') }}
+        run: |
+          tee -a ${GITHUB_ENV} <<<"DC=${DMD}"
+          # Linking errors without -allinst
+          # No other easy way to pass this to dub, using DFLAGS in the
+          # environment disables unittests
+          cat <<-EOF | sudo tee -a /etc/dmd.conf
+          [Environment]
+          DFLAGS=-allinst
+          EOF
 
-    - name: 'Build & Test'
-      run: |
-        # Build the project, with its main file included, without unittests
-        dub build --compiler=$DC
-        # Build and run tests, as defined by `unittest` configuration
-        # In this mode, `mainSourceFile` is excluded and `version (unittest)` are included
-        # See https://dub.pm/package-format-json.html#configurations
-        dub test --compiler=$DC
-        # Run tests
-        cd tests && rdmd test
+      - name: 'Build & Test'
+        shell: bash
+        run: |
+          # Build the project, with its main file included, without unittests
+          dub build
+          # Build and run tests, as defined by `unittest` configuration
+          # In this mode, `mainSourceFile` is excluded and `version (unittest)` are included
+          # See https://dub.pm/package-format-json.html#configurations
+          dub test
+          # Run tests
+          cd tests && "${DMD}" -run test.d