[clang] [clang-tools-extra] [flang] [lld] [llvm] [mlir] [CMake] Remove EXPORT_SYMBOLS_FOR_PLUGINS from #102138 (PR #102396)

[Steven Wu via cfe-commits]

cachemeifyoucan wrote:

That looks an unstable test the has been failed before. 

https://github.com/llvm/llvm-project/pull/102396