Index: cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- cmake/modules/HandleLLVMOptions.cmake
+++ cmake/modules/HandleLLVMOptions.cmake
@@ -131,7 +131,7 @@

 # Pass -Wl,-z,defs. This makes sure all symbols are defined. Otherwise a DSO
 # build might work on ELF but fail on MachO/COFF.
-if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin" OR WIN32 OR
+if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin" OR WIN32 OR CYGWIN
         ${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD") AND
    NOT LLVM_USE_SANITIZER)
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-z,defs")