[clang] [clang]Implement the c23 stdc bit builtins (PR #185978)

[NagaChaitanya Vellanki via cfe-commits]

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@@ -797,6 +797,90 @@ def StdcRotateRight : Builtin {
   let Prototype = "void(...)";
 }
 
+def StdcLeadingZeros: Builtin {
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chaitanyav wrote:

@AaronBallman I have added the LibBuiltin spellings, please review.

https://github.com/llvm/llvm-project/pull/185978