[clang] [Clang] Add __has_target_builtin macro (PR #126324)

[Nick Sarnie via cfe-commits]

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@@ -357,6 +357,7 @@ void Preprocessor::RegisterBuiltinMacros() {
   Ident__has_builtin = RegisterBuiltinMacro("__has_builtin");
   Ident__has_constexpr_builtin =
       RegisterBuiltinMacro("__has_constexpr_builtin");
+  Ident__has_target_builtin = RegisterBuiltinMacro("__has_target_builtin");
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sarnex wrote:

made it unconditional again in the latest commit

i kept the code example in langref because probably we still want to recommend only using this for offloading targets, even though it will work on non-offloading targets. let met know if you disagree.

https://github.com/llvm/llvm-project/pull/126324