kpatch-gcc: use relative path when filtering objects to ignore

When building out-of-tree modules, gcc may be passed full source
pathnames (like /home/user/testmod/testmod.c).  Adjust the filepath
filtering in kpatch-gcc to match against files relative to the
KPATCH_GCC_SRCDIR / kpatch-build SRCDIR prefix.

Fixes: dynup#941
Signed-off-by: Joe Lawrence <[email protected]>

Author: joe-lawrence

kpatch-build/kpatch-gcc

@@ -24,7 +24,7 @@ if [[ "$TOOLCHAINCMD" = "gcc" ]] ; then
 
 			[[ "$obj" = */.tmp_*.o ]] && obj="${obj/.tmp_/}"
 			relobj=${obj//$KPATCH_GCC_SRCDIR\//}
-			case "$obj" in
+			case "$relobj" in
 				*.mod.o|\
 				*built-in.o|\
 				*built-in.a|\