Bump GCC to 15 in Linux CI jobs

Author: victoryforce

.github/workflows/ci.yml

@@ -60,7 +60,7 @@ jobs:
         distro:
           - "ubuntu:25.04"
         compiler:
-          - { compiler: GNU14,  CC: gcc-14,   CXX: g++-14,     packages: gcc-14 g++-14 }
+          - { compiler: GNU15,  CC: gcc-15,   CXX: g++-15,     packages: gcc-15 g++-15 }
           - { compiler: LLVM19, CC: clang-19, CXX: clang++-19, packages: clang-19 libomp-19-dev llvm-19-dev libc++-19-dev libc++abi1-19 lld-19 clang-tools-19 mlir-19-tools libmlir-19-dev}
         btype:
           - Release
@@ -73,7 +73,7 @@ jobs:
           # We want one run in CI to be Debug to make sure the Debug build isn't broken
           - distro: "ubuntu:25.04"
             btype: Debug
-            compiler: { compiler: GNU14, CC: gcc-14, CXX: g++-14, packages: gcc-14 g++-14 }
+            compiler: { compiler: GNU15, CC: gcc-15, CXX: g++-15, packages: gcc-15 g++-15 }
             target: skiptest
             generator: Ninja
             eco: -DDONT_USE_INTERNAL_LIBRAW=OFF