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

[Sergei Barannikov via llvm-commits]

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

(nitpicking)
On a second thought, it might be guarded the same way the `dl_iterate_phdr` use is guarded, that is
```
#if ENABLE_BACKTRACES && defined(HAVE_BACKTRACE) &&                            \
    (defined(__linux__) || defined(__FreeBSD__) ||                             \
     defined(__FreeBSD_kernel__) || defined(__NetBSD__))
```
This would avoid inclusion of `<link.h>` when unnecessary.


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