[LLVM][Cygwin] Fix symbol visibility definition

Author: mati865

llvm/tools/llvm-shlib/CMakeLists.txt

@@ -61,7 +61,7 @@ if(LLVM_BUILD_LLVM_DYLIB)
         # Solaris ld does not accept global: *; so there is no way to version *all* global symbols
         set(LIB_NAMES -Wl,--version-script,${LLVM_LIBRARY_DIR}/tools/llvm-shlib/simple_version_script.map ${LIB_NAMES})
       endif()
-      if (NOT MINGW AND NOT LLVM_LINKER_IS_SOLARISLD_ILLUMOS)
+      if (NOT (MINGW OR CYGWIN) AND NOT LLVM_LINKER_IS_SOLARISLD_ILLUMOS)
         # Optimize function calls for default visibility definitions to avoid PLT and
         # reduce dynamic relocations.
         # Note: for -fno-pic default, the address of a function may be different from