diff --git a/compiler-rt/cmake/config-ix.cmake b/compiler-rt/cmake/config-ix.cmake
--- a/compiler-rt/cmake/config-ix.cmake
+++ b/compiler-rt/cmake/config-ix.cmake
@@ -32,7 +32,9 @@
     list(APPEND CMAKE_REQUIRED_LIBRARIES c)
   endif ()
   if (COMPILER_RT_USE_BUILTINS_LIBRARY)
-    list(APPEND CMAKE_REQUIRED_LIBRARIES "${COMPILER_RT_BUILTINS_LIBRARY}")
+    if (${COMPILER_RT_BUILTINS_LIBRARY})
+      list(APPEND CMAKE_REQUIRED_LIBRARIES "${COMPILER_RT_BUILTINS_LIBRARY}")
+    endif()
   elseif (COMPILER_RT_HAS_GCC_S_LIB)
     list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s)
   elseif (COMPILER_RT_HAS_GCC_LIB)
@@ -42,7 +44,9 @@
     # Mingw64 requires quite a few "C" runtime libraries in order for basic
     # programs to link successfully with -nodefaultlibs.
     if (COMPILER_RT_USE_BUILTINS_LIBRARY)
-      set(MINGW_RUNTIME ${COMPILER_RT_BUILTINS_LIBRARY})
+      if (${COMPILER_RT_BUILTINS_LIBRARY})
+        set(MINGW_RUNTIME ${COMPILER_RT_BUILTINS_LIBRARY})
+      endif()
     else ()
       set(MINGW_RUNTIME gcc_s gcc)
     endif()