Don't use -Werror yet, needs to be restricted to the offload build

Author: dpalermo

flang-rt/lib/runtime/CMakeLists.txt

@@ -12,7 +12,7 @@ find_package(Backtrace)
 set(HAVE_BACKTRACE ${Backtrace_FOUND})
 set(BACKTRACE_HEADER ${Backtrace_HEADER})
 
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
+# set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
 
 # List of files that are buildable for all devices.
 set(supported_sources