vcontainer: add BBMASK for parse savings and suppress layer warnings

The initial vcontainer distro had no BBMASK at all, making it
effectively poky with fewer DISTRO_FEATURES. Every multiconfig parsed
the entire recipe universe even though container image builds only
need a small subset. With 4+ multiconfigs, the parse overhead is
significant.

Add vcontainer-bbmask.inc as a lighter alternative to vruntime's
aggressive BBMASK. It masks the same categories irrelevant to any
container/VM build (graphics, multimedia, desktop, virtualization
platforms, orchestration tools, meta-python, meta-filesystems,
meta-webserver) but keeps the OCI tooling that vruntime blocks:
umoci, container-registry, image recipes, sloci, oci-image-tools.

Masking entire layers (meta-python, meta-filesystems, meta-webserver)
produces BBFILE_PATTERN warnings because the layers are registered in
bblayers.conf (shared with the main build) but have zero recipes after
masking. BitBake provides BBFILE_PATTERN_IGNORE_EMPTY_<collection>
to suppress this, but checks it on self.data (the base datastore),
not per-multiconfig datastores. Setting it in the distro config has
no effect. Move the suppression to meta-virt-host.conf which is
included by the main build's local.conf and therefore visible to
the base datastore.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/docs/build-profiles.md b/docs/build-profiles.md
index 15c4a9cf..7a82855f 100644
--- a/docs/build-profiles.md
+++ b/docs/build-profiles.md
@@ -232,12 +232,17 @@ The `myapp-container.bb` recipe must inherit `image-oci` and produce OCI output.
 | | vruntime | vcontainer |
 |--|----------|------------|
 | **Purpose** | VM rootfs for vdkr/vpdmn | OCI container images |
-| **BBMASK** | Yes (minimal) | No (full packages) |
+| **BBMASK** | Aggressive (blocks OCI tools) | Lighter (keeps OCI tools) |
 | **Init** | busybox | (per recipe) |
 | **IMAGE_FSTYPES** | ext4 | (per recipe) |
 | **Multiconfigs** | vruntime-aarch64, vruntime-x86-64 | container-aarch64, container-x86-64 |
 | **Shared base** | vruntime-base.inc | vruntime-base.inc |
 
+Both distros mask graphics, multimedia, desktop, virtualization platforms,
+and orchestration tools. The difference is that vruntime additionally masks
+OCI tooling (umoci, container-registry, image recipes, sloci) that
+vcontainer needs for building container images.
+
 ## Design Notes
 
 **Profiles are pure deltas.** They do not include `meta-virt-host.conf`