Add GHA job with GCC 15

Author: Flamefire

.github/workflows/unit-tests.yml

@@ -78,7 +78,7 @@ jobs:
           - { compiler: clang,    os: macos-14,     type: Debug }
 
           # Linux:
-          #  Oldest Compilers 
+          #  Oldest Compilers
           #   GCC 9 also known to show a few warnings that newer versions dont show
           #   Use system cmake
           #   Use boost 1.73 (min version)
@@ -105,11 +105,13 @@ jobs:
           #   Use default boost
           #   Use (compiler) default C++ 17 standard
           #   Use default cmake
-          - { compiler: gcc-14,   os: ubuntu-24.04, type: Debug }
-          - { compiler: clang-18, os: ubuntu-24.04, type: Debug, externalSanitizer: true }
-          - { compiler: clang-21, os: ubuntu-latest, type: Debug, init_llvm: true}
+          - { compiler: gcc-14,   os: ubuntu-24.04,          type: Debug }
+          - { compiler: gcc-15,   container: "ubuntu:25.04", type: Debug, os: ubuntu-latest }
+          - { compiler: clang-18, os: ubuntu-24.04,          type: Debug, externalSanitizer: true }
+          - { compiler: clang-21, os: ubuntu-latest,         type: Debug, init_llvm: true}
 
     runs-on: ${{matrix.os}}
+    container: ${{matrix.container}}
 
     steps:
       - name: Setup env and configure flags
@@ -171,6 +173,10 @@ jobs:
             find "$BOOST_ROOT"/lib/cmake -type f
             echo "BOOST_ROOT=${BOOST_ROOT}" >> $GITHUB_ENV
           else
+            if [ -n "${{matrix.container}}" ] && [ -f "/etc/debian_version" ]; then
+              apt-get -o Acquire::Retries=5 update
+              apt-get -o Acquire::Retries=5 -y -q --no-install-suggests --no-install-recommends install sudo software-properties-common
+            fi
             compiler=${{matrix.compiler}}
             compiler=${compiler/gcc-/g++-}
             if [[ "${{matrix.init_llvm}}" == "true" ]]; then