Index: cmake/config-ix.cmake
===================================================================
--- cmake/config-ix.cmake
+++ cmake/config-ix.cmake
@@ -168,7 +168,12 @@
 endif()
 
 # Generate the COMPILER_RT_SUPPORTED_ARCH list.
-if(ANDROID)
+if(NOT COMPILER_RT_BUILD_SANITIZERS AND CMAKE_C_COMPILER_FORCED)
+  # If the compiler has been forced and we build only the builtins library
+  # assume that the arch is supported.
+  set(CAN_TARGET_${COMPILER_RT_DEFAULT_TARGET_ARCH} 1)
+  list(APPEND COMPILER_RT_SUPPORTED_ARCH ${COMPILER_RT_DEFAULT_TARGET_ARCH})
+elseif(ANDROID)
   # Examine compiler output to determine target architecture.
   detect_target_arch()
   set(COMPILER_RT_OS_SUFFIX "-android")