Index: llvm/cmake/modules/LLVMExternalProjectUtils.cmake
===================================================================
--- llvm/cmake/modules/LLVMExternalProjectUtils.cmake
+++ llvm/cmake/modules/LLVMExternalProjectUtils.cmake
@@ -318,6 +318,13 @@
                -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
                -DCMAKE_C_COMPILER_LAUNCHER=${CMAKE_C_COMPILER_LAUNCHER}
                -DCMAKE_CXX_COMPILER_LAUNCHER=${CMAKE_CXX_COMPILER_LAUNCHER}
+               -DCMAKE_C_FLAGS=${CMAKE_C_FLAGS}
+               -DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS}
+               -DCMAKE_EXE_LINKER_FLAGS=${CMAKE_EXE_LINKER_FLAGS}
+               -DCMAKE_SHARED_LINKER_FLAGS=${CMAKE_SHARED_LINKER_FLAGS}
+               -DCMAKE_MODULE_LINKER_FLAGS=${CMAKE_MODULE_LINKER_FLAGS}
+               -DCMAKE_OSX_DEPLOYMENT_TARGET=${CMAKE_OSX_DEPLOYMENT_TARGET}
+               -DCMAKE_OSX_ARCHITECTURES=${CMAKE_OSX_ARCHITECTURES}
                -DCMAKE_EXPORT_COMPILE_COMMANDS=1
                ${cmake_args}
                ${PASSTHROUGH_VARIABLES}