PV-GRUB: Check for errors when applying patches to GRUB

We want to ensure that patches apply cleanly without rejects. Bail if
patch returns a non-zero exit code.

Signed-off-by: Matt Wilson <msw@amazon.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

stubdom/Makefile

@@ -331,7 +331,7 @@ grub-upstream: grub-$(GRUB_VERSION).tar.gz
 	tar xzf $<
 	mv grub-$(GRUB_VERSION) $@
 	for i in grub.patches/* ; do \
-		patch -d $@ -p1 < $$i ; \
+		patch -d $@ -p1 < $$i || exit 1; \
 	done
 
 .PHONY: grub