[compiler-rt] [compiler-rt] Add initial ARM64EC builtins support (PR #139279)

[Jacek Caban via llvm-commits]

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@@ -122,7 +123,7 @@ void __clear_cache(void *start, void *end) {
     compilerrt_abort();
 #endif
   }
-#elif defined(__aarch64__) && !defined(__APPLE__)
+#elif (defined(__aarch64__) || defined(__arm64ec__)) && !defined(__APPLE__)
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cjacek wrote:

Good point, I think this is redundant. This came from Billy's original patch. I remember changing a similar case elsewhere but missed this one.

https://github.com/llvm/llvm-project/pull/139279