[clang] [NFC] Move warning from CodeGen to Sema. (PR #107397)

[Joshua Cranmer via cfe-commits]

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@@ -6784,6 +6784,12 @@ def warn_arc_lifetime_result_type : Warning<
   "ARC %select{unused|__unsafe_unretained|__strong|__weak|__autoreleasing}0 "
   "lifetime qualifier on return type is ignored">,
   InGroup<IgnoredQualifiers>;
+def warn_excess_precision_not_supported : Warning<
+  "excess precision is requested but the target does not support excess "
+  "precision which may result in observable differences in complex division "
+  "behavior%select{|,additional uses where the requested higher precision "
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jcranmer-intel wrote:

Nit: space after the comma?

https://github.com/llvm/llvm-project/pull/107397