[brief] Adding MacOS to the testing matrix.

[detailed]
- I'm starting with Clang first because I'm almost sure it won't
  compile.

.github/workflows/build.yml

@@ -36,6 +36,7 @@ jobs:
           - {os: "windows-latest", cxx: "msvc", cc: "msvc", preset: "msvc"}
           - {os: "ubuntu-24.04", cxx: "clang++-18", cc: "clang-18", preset: "clang"}
           - {os: "ubuntu-24.04", cxx: "g++-14", cc: "gcc-14", preset: "gcc"}
+          - {os: "macos-latest", cxx: "clang++", cc: "clang", preset: "apple"}
         build: ["Debug", "Release"]
     steps:
       - name: Chekout

CMakePresets.json

@@ -55,7 +55,7 @@
             "description": "Default build for Apple platforms",
             "inherits": "unix_base",
             "cacheVariables": {
-                "CMAKE_CXX_FLAGS": "-Wall -Wextra -pedantic -Werror"
+                "CMAKE_CXX_FLAGS": "-Wall -Wextra -pedantic -Werror -stdlib=libstdc++"
             }
         }
     ]