buildah: address uncovered checkton warnings

The '... -t $IMAGE' line changed, making checkton report the violations
on this line:

- $IMAGE needs quotes (valid)
- $IMAGE is a potential misspelling of $image (not valid, IMAGE is
  defined externally but checkton doesn't know that)

Signed-off-by: Adam Cmiel <[email protected]>

task/buildah/0.2/buildah.yaml

@@ -353,15 +353,18 @@ spec:
         done < <(find $ADDITIONAL_SECRET_TMP -maxdepth 1 -type f -exec basename {} \;)
       fi
 
+      # Prevent ShellCheck from giving a warning because 'image' is defined and 'IMAGE' is not.
+      declare IMAGE
+
       unshare -Uf $UNSHARE_ARGS --keep-caps -r --map-users 1,1,65536 --map-groups 1,1,65536 -w ${SOURCE_CODE_DIR}/$CONTEXT -- buildah build \
         $VOLUME_MOUNTS \
         "${BUILDAH_ARGS[@]}" \
         "${LABELS[@]}" \
         --tls-verify=$TLSVERIFY --no-cache \
         --ulimit nofile=4096:4096 \
-        -f "$dockerfile_copy" -t $IMAGE .
+        -f "$dockerfile_copy" -t "$IMAGE" .
 
-      container=$(buildah from --pull-never $IMAGE)
+      container=$(buildah from --pull-never "$IMAGE")
       buildah mount $container | tee /shared/container_path
       # delete symlinks - they may point outside the container rootfs, messing with SBOM scanners
       find $(cat /shared/container_path) -xtype l -delete