Exclude ubuntu + gcc-15

Author: jvdp1

.github/workflows/CI.yml

@@ -44,6 +44,8 @@ jobs:
             toolchain: {compiler: intel, version: '2024.1'}
           - os: macos-14
             toolchain: {compiler: gcc, version: 10}
+          - os: ubuntu-latest
+            toolchain: {compiler: gcc, version: 15}
     env:
       BUILD_DIR: ${{ matrix.build == 'cmake' && 'build' || '.' }}