[ASan] Fix Windows build by excluding asan_rtl_x86_64.S.

compiler-rt/lib/asan/CMakeLists.txt

set(ASAN_SOURCES
   asan_malloc_mac.cpp
   asan_malloc_win.cpp
   asan_memory_profile.cpp
   asan_poisoning.cpp
   asan_posix.cpp
   asan_premap_shadow.cpp
   asan_report.cpp
   asan_rtl.cpp
-  asan_rtl_x86_64.S
   asan_shadow_setup.cpp
   asan_stack.cpp
   asan_stats.cpp
   asan_suppressions.cpp
   asan_thread.cpp
   asan_win.cpp
   )
 
 if (NOT WIN32 AND NOT APPLE)
   list(APPEND ASAN_SOURCES
+    asan_rtl_x86_64.S
     asan_interceptors_vfork.S
     )
 endif()
 
 set(ASAN_CXX_SOURCES
   asan_new_delete.cpp
   )