Make bundle generation work during merges

This is required for openshift-service-mesh#14

Signed-off-by: Daniel Grimm <dgrimm@redhat.com>

Makefile.core.mk

@@ -461,7 +461,7 @@ bundle: gen helm operator-sdk ## Generate bundle manifests and metadata, then va
 		if (git ls-files --error-unmatch "$$csvPath" &>/dev/null); then \
 			if ! (git diff "$$csvPath" | grep '^[+-][^+-][^+-]' | grep -v "createdAt:" >/dev/null); then \
 				echo "reverting timestamp change in $$csvPath"; \
-				git checkout "$$csvPath"; \
+				git checkout "$$csvPath" || echo "failed to revert timestamp change. assuming we're in the middle of a merge"; \
 			fi \
 		fi
 	$(OPERATOR_SDK) bundle validate ./bundle