[llvm] [CMake] Remove HAVE_LINK_H (PR #104893)

[Fangrui Song via llvm-commits]

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@@ -65,7 +65,7 @@
 #ifdef __APPLE__
 #include <mach-o/dyld.h>
 #endif
-#if HAVE_LINK_H
+#if __has_include(<link.h>)
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MaskRay wrote:

Thought about this. Since the include and its only use site are very far apart, I prefer to stick with the simple `__has_include` (C++17, should be in all supported compilers)

https://github.com/llvm/llvm-project/pull/104893