[CMake] export_executable_symbols also needs to add -rdynamic to the linker flags on Darwin

Without -rdynamic LLVM built with LTO fails to pass "check" due to loadable modules failing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253944 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed