fix: skip herokuish version in report output and disable the herokuish builder on armhf architectures

We don't skip pack as in theory they may be able to support arm in the future. Dockerfile builds should work fine, as long as all images in the FROM directives have arm versions.
Finally, the null builder _should_ always work, but of course YMMV :D

plugins/builder-herokuish/builder-detect

@@ -8,6 +8,10 @@ trigger-builder-herokuish-builder-detect() {
   declare trigger="builder-detect"
   declare APP="$1" SOURCECODE_WORK_DIR="$2"
 
+  if [[ "$(dpkg --print-architecture 2>/dev/null || true)" == "armhf" ]]; then
+    return
+  fi
+
   if fn-has-buildpacks-file "$SOURCECODE_WORK_DIR"; then
     echo "herokuish"
     return