- for extern inline, also take __extern_inline and __GNUC_GNU_INLINE__ into account

include/features.h

@@ -367,7 +367,8 @@
 
 /* Decide whether we can define 'extern inline' functions in headers.  */
 #if __GNUC_PREREQ (2, 7) && defined __OPTIMIZE__ \
-    && !defined __OPTIMIZE_SIZE__ && !defined __NO_INLINE__
+    && !defined __OPTIMIZE_SIZE__ && !defined __NO_INLINE__ \
+    && (defined __extern_inline || defined __GNUC_GNU_INLINE__)
 # define __USE_EXTERN_INLINES	1
 #endif