[clang] [flang] [flang] Add checks for Fortran 2023 system clock and add f2023/f202Y to valid arguments of -std= (PR #205938)

[via cfe-commits]

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@@ -60,7 +60,8 @@ ENUM_CLASS(LanguageFeature, BackslashEscapes, OldDebugLines,
     DefaultStructConstructorNullPointer, AssumedRankIoItem,
     MultipleProgramUnitsOnSameLine, AllocatedForAssociated,
     OpenMPThreadprivateEquivalence, RelaxedCLocChecks, CudaPinned,
-    OpenAccDefaultNoneScalarsStrict, OpenACCMultipleNamesInRoutine)
+    OpenAccDefaultNoneScalarsStrict, OpenACCMultipleNamesInRoutine,
+    SystemClockStrict)
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chris-earl wrote:

Good catch! This is not the intended behavior. I have fixed this. See my comments below.

https://github.com/llvm/llvm-project/pull/205938