buildgcc: Apply patches with -p1

Turned out that there are versions of the patch command that use the
left hand side path for new files created by a patch. This behavior is
incompatible with some of our patches. Stripping the topmost dir from
the path with -p1 helps.

While touching that line, I couldn't resist to drop a command
substituion (the `echo $patch`). It really shouldn't be necessary as the
path to the patch file is already expanded in the head of the for loop.

Change-Id: I95398605db6dd54a8b08d8bc84c6602edbea6e10
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/15908
Reviewed-by: Idwer Vollering <vidwer@gmail.com>
Tested-by: build bot (Jenkins)

util/crossgcc/buildgcc

@@ -269,7 +269,7 @@ unpack_and_patch() {
 		for patch in patches/${dir}_*.patch; do
 			test -r $patch || continue
 			printf "   o $(basename $patch)\n"
-			$PATCH -s -N -p0 < $(echo $patch) || {
+			(cd ${dir} && $PATCH -s -N -p1 <../${patch}) || {
 				printf "\n${RED}Failed $patch.${NC}\n"
 				exit 1
 			}