GCE: Specify the architecture of images

Without a specified architecture, a user can attempt to create an
arm64 instance with an amd64 image or vice versa. With the change
the API will prevent that mismatch.

release/Makefile.gce

@@ -15,6 +15,14 @@ CLEANFILES+=		${GCE_UPLOAD_TGTS}
 GCE_BUCKET?=
 GCE_LICENSE?=
 
+.if ${TARGET_ARCH} == "amd64"
+GCE_ARCH=		X86_64
+.elif ${TARGET_ARCH} == "aarch64"
+GCE_ARCH=		ARM64
+.else
+.error "Unsupported TARGET_ARCH for GCE: ${TARGET_ARCH}. Must be amd64 or aarch64."
+.endif
+
 .if !defined(GCE_FAMILY) || empty(GCE_FAMILY)
 GCE_FAMILY=		${TYPE:tl}-${REVISION:S,.,-,}-${TARGET}
 .endif
@@ -74,6 +82,7 @@ gce-do-upload-${_FS}:
 	/usr/local/bin/gsutil cp ${.OBJDIR}/${GCE_TARGET_${_FS}}.tar.gz \
 		gs://${GCE_BUCKET}/
 	/usr/local/bin/gcloud compute images create ${GCE_TARGET_${_FS}} \
+		--architecture=${GCE_ARCH} \
 		--family=${GCE_FAMILY}-${_FS}${GCE_FAMILY_SUFX} ${GCE_LICENSE} \
 		--guest-os-features=GVNIC,UEFI_COMPATIBLE \
 		--source-uri gs://${GCE_BUCKET}/${GCE_TARGET_${_FS}}.tar.gz