[clang] [Clang][z/OS] Add CSECT option and pragma (PR #234368)

[Sean Perry via cfe-commits]

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@@ -5650,6 +5650,44 @@ The builtins return 0 if the values are equal, or 1 if they are unequal.
 
   Generates a 16-byte compare-and-swap using the CDSG instruction.
 
+#### z/OS CSECT pragma
+
+Clang supports the `-mcsect`, `-mcsect=<qualifier>`, and `-mno-csect` options,
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perry-ca wrote:

It's good/important to have the option documentation.  Can you find somewhere to put the documentation for the -mcsect options.   Having it under the pragma descriptions seems like it will get lost or not found.

https://github.com/llvm/llvm-project/pull/234368