Add compiler flags for gcc-15 to suppress specific warnings

Author: texasich

.github/workflows/build.yml

@@ -70,6 +70,7 @@ jobs:
           -D CMAKE_C_COMPILER_LAUNCHER=ccache
           -D CMAKE_CXX_COMPILER_LAUNCHER=ccache
           -DCMAKE_POLICY_VERSION_MINIMUM=3.5
+          ${{ matrix.cc == 'gcc-15' && '-DCMAKE_CXX_FLAGS=-Wno-error=missing-declarations -Wno-error=missing-field-initializers' || '' }}
 
       - name: Build
         run: cmake --build ${{ github.workspace }}/build --preset ${{ matrix.preset }} --config ${{ matrix.build_type }} -j 4