Index: cmake/base-config-ix.cmake
===================================================================
--- cmake/base-config-ix.cmake
+++ cmake/base-config-ix.cmake
@@ -113,6 +113,7 @@
 
   # Generate the COMPILER_RT_SUPPORTED_ARCH list.
   if(ANDROID)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${CMAKE_CFLAGS}")
     # Examine compiler output to determine target architecture.
     detect_target_arch()
     set(COMPILER_RT_OS_SUFFIX "-android")
Index: lib/builtins/CMakeLists.txt
===================================================================
--- lib/builtins/CMakeLists.txt
+++ lib/builtins/CMakeLists.txt
@@ -407,12 +407,11 @@
           list(REMOVE_ITEM ${arch}_SOURCES ${_cname})
         endif ()
       endforeach ()
-
       add_compiler_rt_runtime(clang_rt.builtins
                               STATIC
                               ARCHS ${arch}
                               SOURCES ${${arch}_SOURCES}
-                              CFLAGS ${maybe_stdc99}
+                              CFLAGS ${maybe_stdc99} ${CMAKE_CFLAGS}
                               PARENT_TARGET builtins)
     endif ()
   endforeach ()