[clang] [llvm] [CMake] Add a linker test for -Bsymbolic-functions to AddLLVM (PR #79539)

[Fangrui Song via cfe-commits]

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@@ -355,6 +349,9 @@ function(add_link_opts target_name)
     set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                  LINK_FLAGS " -Wl,-brtl")
   endif()
+
+  check_linker_flag(CXX "-Wl,-Bsymbolic-functions"
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MaskRay wrote:

@mati865 This might be true for other, smaller projects, but for LLVM we have to be careful introducing new checks. https://discourse.llvm.org/t/cmake-compiler-flag-checks-are-really-slow-ideas-to-speed-them-up/78882
It could be slower on a slow device like NFS. For this single check_linker_flag it might be fine.

https://github.com/llvm/llvm-project/pull/79539