[CMake] Split -gx strip flag into -g -x

llvm-strip doesn't handle -gx spelling, so we need to split these
as two separate flags.

Differential Revision: https://reviews.llvm.org/D50684

llvm-svn: 339639
diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index 24ef5e4..b68de99 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -1566,7 +1566,7 @@
       endif()
       set(strip_command COMMAND ${CMAKE_STRIP} -Sxl $<TARGET_FILE:${name}>)
     else()
-      set(strip_command COMMAND ${CMAKE_STRIP} -gx $<TARGET_FILE:${name}>)
+      set(strip_command COMMAND ${CMAKE_STRIP} -g -x $<TARGET_FILE:${name}>)
     endif()
   endif()