Promote a precompiled tag that is missing an architecture

pushImage skipped the push whenever the destination tag already existed,
and imageExists only asked regctl whether the tag resolved at all.
regctl manifest get --list succeeds for any manifest list, no matter
which platforms it contains, and FORCE_PUSH is not set anywhere in this
repository, so the skip always won.

That is harmless while a distribution is amd64 only, but ubuntu24.04 and
now ubuntu26.04 build both architectures. Once an amd64-only tag existed
at the destination, the arm64 instance could never be published: every
later run saw the tag, skipped, and reported success.

The check now probes each platform the build targets with regctl
manifest get --platform, which fails when the manifest list has no entry
for it, and pushes when any of them is missing. push runs as a separate
invocation from build, so the platform set has to be recomputed rather
than carried over; both paths now read it from targetPlatforms so they
cannot disagree about which distributions and kernel flavors are
multi-arch.

Distributions that stay single-arch keep the old behaviour, since
targetPlatforms is empty for them and only the tag existence check runs.

Signed-off-by: Abrar Shivani <ashivani@nvidia.com>

Author: abrarshivani

scripts/precompiled.sh

@@ -41,11 +41,19 @@ function buildBaseImage(){
     make DRIVER_BRANCH=${DRIVER_BRANCH} KERNEL_FLAVOR=${KERNEL_FLAVOR} build-base-${BASE_TARGET}
 }
 
-function buildImage(){
+function targetPlatforms(){
     # linux-objects-nvidia-*-azure-fde is published for amd64 only.
     if [[ "$DIST" == "signed_ubuntu24.04" || "$DIST" == "signed_ubuntu26.04" ]] \
        && [[ "$KERNEL_FLAVOR" != "azure-fde" ]]; then
-        export DOCKER_BUILD_PLATFORM_OPTIONS="--platform=linux/amd64,linux/arm64"
+        echo "linux/amd64 linux/arm64"
+    fi
+}
+
+function buildImage(){
+    local platforms
+    platforms=$(targetPlatforms)
+    if [ -n "$platforms" ]; then
+        export DOCKER_BUILD_PLATFORM_OPTIONS="--platform=${platforms// /,}"
     fi
     make DRIVER_VERSIONS=${DRIVER_VERSIONS} DRIVER_BRANCH=${DRIVER_BRANCH} build-${DIST}-${DRIVER_VERSION}
 }
@@ -63,7 +71,7 @@ function pushImage(){
 	# note: DIST is in the form "signed_<distribution>", so we drop the '*_' prefix
 	# to extract the distribution string.
 	local out_image=${OUT_IMAGE_NAME}:${DRIVER_BRANCH}-${KERNEL_VERSION}-${DIST##*_}
-	if imageExists "$out_image"; then
+	if imageExistsForAllTargetPlatforms "$out_image"; then
 		echo "image tag already exists in output registry - $out_image"
 		if [ "$FORCE_PUSH" != "true" ]; then
 			echo "exiting"
@@ -89,6 +97,17 @@ function imageExists(){
 	regctl manifest get $1 --list > /dev/null && return 0 || return 1
 }
 
+function imageExistsForAllTargetPlatforms(){
+	local image=$1
+	imageExists "$image" || return 1
+	local platform
+	for platform in $(targetPlatforms); do
+		# unlike --list, --platform fails when the manifest list carries no entry for that platform
+		regctl manifest get "$image" --platform "$platform" > /dev/null || return 1
+	done
+	return 0
+}
+
 case $1 in
     build)
         buildBaseImage