Squashed 'release-tools/' changes from 7bc70e52..1748b16b

1748b16b Merge pull request #136 from pohly/go-1.16
ec844ea6 remove travis.yml, Go 1.16
df76aba8 Merge pull request #134 from andyzhangx/add-build-arg
e314a56d add build-arg ARCH for building multi-arch images, e.g. ARG ARCH FROM k8s.gcr.io/build-image/debian-base-${ARCH}:v2.1.3

git-subtree-dir: release-tools
git-subtree-split: 1748b16b488381c34a86ddbee110e9ed523bcb20

build.make

@@ -149,6 +149,7 @@ $(CMDS:%=push-multiarch-%): push-multiarch-%: check-pull-base-ref build-%
 				--platform=$$os/$$arch \
 				--file $$(eval echo \$${dockerfile_$$os}) \
 				--build-arg binary=./bin/$*$$suffix \
+				--build-arg ARCH=$$arch \
 				--label revision=$(REV) \
 				.; \
 		done; \