[ci] Adapt compilation tests to support Windows

Author: ricab

.github/workflows/test.yml

@@ -83,6 +83,17 @@ jobs:
     - name: Determine number of cpus on Windows
       if: startsWith(matrix.os, 'windows')
       run: echo "num_cpus=$env:NUMBER_OF_PROCESSORS" >> $env:GITHUB_ENV
+
+    - name: Determine number of compilation test jobs on macOS and Linux
+      if: ${{ !startsWith(matrix.os, 'windows') }}
+      shell: bash
+      run: echo "num_comp_tests=$((${{env.num_cpus}} * 2))" >> $GITHUB_ENV
+
+    - name: Determine number of compilation test jobs on Windows
+      if: startsWith(matrix.os, 'windows')
+      shell: bash
+      run: echo "num_comp_tests=1" >> $GITHUB_ENV
+
     - name: Determine compiler flag
       if: ${{matrix.compiler}}
       run: echo "CXX=${{matrix.compiler}}" >> $GITHUB_ENV
@@ -97,10 +108,8 @@ jobs:
 
     - name: Test
       working-directory: ${{github.workspace}}/build
-      run: cmake --build . --config ${BUILD_TYPE} --target test
-        ARGS=-j$((${num_cpus} * 2)) # don't pass --parallel, which would affect compilation tests,
-                                    # but do run twice as many compilation tests as the number of
-                                    # available threads
+      run: cmake --build . --config ${{env.BUILD_TYPE}} --target test
+        ARGS=-j${{env.num_comp_tests}} # don't pass --parallel, which would affect compilation tests
 
     - name: Produce coverage reports
       if: contains(matrix.extra_build_flags, 'coverage')