[libcxx] [llvm] [libc++] Updates the compilers used post LLVM-20 branching. (PR #126564)

[Nikolas Klauser via llvm-commits]

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@@ -88,18 +88,22 @@ jobs:
           'generic-cxx20',
           'generic-cxx23'
         ]
-        cc: [ 'clang-20' ]
-        cxx: [ 'clang++-20' ]
+        cc: [ 'clang-21' ]
+        cxx: [ 'clang++-21' ]
         include:
           - config: 'generic-gcc-cxx11'
             cc: 'gcc-14'
             cxx: 'g++-14'
-          - config: 'generic-cxx23'
-            cc: 'clang-18'
-            cxx: 'clang++-18'
+          - config: 'generic-cxx26'
+            cc: 'clang-20'
+            cxx: 'clang++-20'
           - config: 'generic-cxx26'
             cc: 'clang-19'
             cxx: 'clang++-19'
+          # Release transition
+          - config: 'generic-cxx23'
+            cc: 'clang-18'
+            cxx: 'clang++-18'
----------------
philnik777 wrote:

I don't remember any rules on this and I though it was around for quite a while sometimes. If we agree that it can go after the initial release I'm fine with it, but I really don't want to keep it around for the whole cycle, since that would effectively extend our supported compilers by one version.

https://github.com/llvm/llvm-project/pull/126564