fix image name during build (#1968)

Makefile

@@ -44,14 +44,18 @@ HELM_CHART_NAME ?= "aws-vpc-cni"
 TEST_IMAGE = amazon-k8s-cni-test
 TEST_IMAGE_NAME = $(TEST_IMAGE)$(IMAGE_ARCH_SUFFIX):$(VERSION)
 
+UNAME_ARCH = $(shell uname -m)
+ARCH = $(lastword $(subst :, ,$(filter $(UNAME_ARCH):%,x86_64:amd64 aarch64:arm64)))
+# This is only applied to the arm64 container image by default. Override to
+# provide an alternate suffix or to omit.
+IMAGE_ARCH_SUFFIX = $(addprefix -,$(filter $(ARCH),arm64))
+
 # Mandate usage of docker buildkit as platform arguments are available only with buildkit
 # Refer to https://docs.docker.com/engine/reference/builder/#automatic-platform-args-in-the-global-scope
 # and https://docs.docker.com/develop/develop-images/build_enhancements/#to-enable-buildkit-builds
 export DOCKER_BUILDKIT=1
 GOARCH = $(TARGETARCH)
-# This is only applied to the arm64 container image by default. Override to
-# provide an alternate suffix or to omit.
-IMAGE_ARCH_SUFFIX = $(addprefix -,$(filter $(GOARCH),arm64))
+
 # GOLANG_IMAGE is the building golang container image used.
 GOLANG_IMAGE = public.ecr.aws/docker/library/golang:1.17-stretch
 # For the requested build, these are the set of Go specific build environment variables.