[clang] [Fuchsia] Build with -fvisibility=default (PR #67067)

[Petr Hosek via cfe-commits]

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@@ -52,6 +52,7 @@ set(ENABLE_LINKER_BUILD_ID ON CACHE BOOL "")
 set(ENABLE_X86_RELAX_RELOCATIONS ON CACHE BOOL "")
 
 set(CMAKE_BUILD_TYPE Release CACHE STRING "")
+set(CMAKE_CXX_VISIBILITY_PRESET default CACHE STRING "")
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petrhosek wrote:

Should we also set `CMAKE_C_VISIBILITY_PRESET` to `default` for consistency?

https://github.com/llvm/llvm-project/pull/67067