compiler-gcc4: conditionalize #error on __KERNEL__

Impact: Fix for exported headers

We only want to error out on specific gcc versions if we are actually
building the kernel, so conditionalize the #if...#error on __KERNEL__.

Based on a patchset by Arnd Bergmann <arnd@arndb.de>.

Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

include/linux/compiler-gcc4.h

@@ -3,8 +3,10 @@
 #endif
 
 /* GCC 4.1.[01] miscompiles __weak */
-#if __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ <= 1
-# error Your version of gcc miscompiles the __weak directive
+#ifdef __KERNEL__
+# if __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ <= 1
+#  error Your version of gcc miscompiles the __weak directive
+# endif
 #endif
 
 #define __used			__attribute__((__used__))