Improve handling of virtual packages and build messages

  - add metadata to distinguish virtual package types
  - improve build order and status messages for empty packages
        print pkg type or `disabled` instead of `no-build`
  - add BUILD_DRY_RUN option and fixup make -t
  - update build-matrix rule to identify virtual pkgs

1 files changed, 4 insertions, 0 deletions

diff --git a/docs/assets/build-matrix.css b/docs/assets/build-matrix.css
index 49850b6..fe47d12 100644
--- a/docs/assets/build-matrix.css
+++ b/docs/assets/build-matrix.css
@@ -12,3 +12,7 @@ td.unsupported {
     background-color: #f99;
     text-align: center;
 }
+td.neutral {
+    background-color: #d1d1d1;
+    text-align: center;
+}