Add AppleClang to CI tests

.github/workflows/macos.yml

@@ -11,25 +11,24 @@ on:
 
 jobs:
   build:
-    runs-on: macos-latest
+    runs-on: macos-15
     strategy:
       matrix:
-        compiler: [GCC-13, LLVM-Clang-16, LLVM-Clang-17, LLVM-Clang-18, LLVM-Clang-19]
+        compiler: [AppleClang, LLVM-Clang-16, LLVM-Clang-17, LLVM-Clang-18, LLVM-Clang-19]
         test_with: [Headers, Module]
         build_type: [Debug, Release]
 
         exclude:
-          - compiler: GCC-13
-        #    test_with: Module
+          - compiler: AppleClang
+            test_with: Module
           - compiler: LLVM-Clang-16
             test_with: Module
 
         include:
-        #  - compiler: GCC-13
-        #    cxx: g++-13
-        #    install: |
-        #      brew update
-        #      brew install gcc@13 ninja
+          - compiler: AppleClang
+            cxx: clang++
+            install: |
+              brew install ninja
           - compiler: LLVM-Clang-16
             cxx: $(brew --prefix llvm@16)/bin/clang++
             install: |

README.md

@@ -80,8 +80,7 @@ Flux requires a recent compiler with good support for the C++20 standard. It is
 * GCC 11.3 and newer
 * LLVM Clang 16 and newer
 * MSVC 2022
-
-AppleClang is currently not usable due to missing C++20 support.
+* AppleClang/Xcode 16
 
 ## The Flux difference ##