vcontainer: enable incremental builds by default

Previously, vcontainer recipes had [nostamp] flags that forced all
tasks to rebuild on every bitbake invocation, even when nothing changed.
This was added as a workaround for dependency tracking issues but caused
slow rebuild times.

Changes:
- Make [nostamp] conditional on VCONTAINER_FORCE_BUILD variable
- Default to normal stamp-based caching for faster incremental builds
- file-checksums on do_rootfs still tracks init script changes
- Add VCONTAINER_FORCE_BUILD status to the tarball build banner

To enable the old always-rebuild behavior (for debugging dependency
issues), set in local.conf:
  VCONTAINER_FORCE_BUILD = "1"

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

4 files changed, 38 insertions, 10 deletions

diff --git a/recipes-containers/vcontainer/vcontainer-initramfs-create.inc b/recipes-containers/vcontainer/vcontainer-initramfs-create.inc
index 00ae5332..b50179d5 100644
--- a/recipes-containers/vcontainer/vcontainer-initramfs-create.inc
+++ b/recipes-containers/vcontainer/vcontainer-initramfs-create.inc
@@ -33,10 +33,17 @@ EXCLUDE_FROM_WORLD = "1"
 # No extraction tools needed - we use pre-built images
 DEPENDS = ""
 
-# Always rebuild - no sstate caching for this recipe
-SSTATE_SKIP_CREATION = "1"
-do_compile[nostamp] = "1"
-do_deploy[nostamp] = "1"
+# Force rebuild control:
+# Set VCONTAINER_FORCE_BUILD = "1" in local.conf to disable stamp caching
+# and force compile/deploy to always run. Useful when debugging dependency issues.
+# Default: use normal stamp caching for faster incremental builds
+VCONTAINER_FORCE_BUILD ?= ""
+python () {
+    if d.getVar('VCONTAINER_FORCE_BUILD') == '1':
+        d.setVar('SSTATE_SKIP_CREATION', '1')
+        d.setVarFlag('do_compile', 'nostamp', '1')
+        d.setVarFlag('do_deploy', 'nostamp', '1')
+}
 
 # Only populate native sysroot, skip target sysroot to avoid libgcc conflicts
 INHIBIT_DEFAULT_DEPS = "1"
diff --git a/recipes-containers/vcontainer/vcontainer-tarball.bb b/recipes-containers/vcontainer/vcontainer-tarball.bb
index 180f3c19..a4e9a9a5 100644
--- a/recipes-containers/vcontainer/vcontainer-tarball.bb
+++ b/recipes-containers/vcontainer/vcontainer-tarball.bb
@@ -144,6 +144,15 @@ python () {
         bb.plain("  To build only one architecture, set in local.conf:")
         bb.plain("    VCONTAINER_ARCHITECTURES = \"x86_64\"")
         bb.plain("    VCONTAINER_ARCHITECTURES = \"aarch64\"")
+        bb.plain("")
+        force = d.getVar('VCONTAINER_FORCE_BUILD') or ''
+        if force == '1':
+            bb.plain("  VCONTAINER_FORCE_BUILD = \"1\" (enabled)")
+            bb.plain("    All vcontainer tasks will rebuild unconditionally.")
+        else:
+            bb.plain("  Incremental builds enabled (default).")
+            bb.plain("    To force full rebuild, set in local.conf:")
+            bb.plain("      VCONTAINER_FORCE_BUILD = \"1\"")
         bb.plain("=" * 70)
         bb.plain("")
 }
diff --git a/recipes-containers/vcontainer/vdkr-rootfs-image.bb b/recipes-containers/vcontainer/vdkr-rootfs-image.bb
index 8dcf4190..0bcf40b6 100644
--- a/recipes-containers/vcontainer/vdkr-rootfs-image.bb
+++ b/recipes-containers/vcontainer/vdkr-rootfs-image.bb
@@ -30,9 +30,15 @@ LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda
 do_rootfs[file-checksums] += "${THISDIR}/files/vdkr-init.sh:True"
 do_rootfs[file-checksums] += "${THISDIR}/files/vcontainer-init-common.sh:True"
 
-# Force do_rootfs to always run (no stamp caching)
-# Combined with file-checksums, this ensures init script changes are picked up
-do_rootfs[nostamp] = "1"
+# Force rebuild control:
+# Set VCONTAINER_FORCE_BUILD = "1" in local.conf to disable stamp caching
+# and force rootfs to always rebuild. Useful when debugging dependency issues.
+# Default: use normal stamp caching (file-checksums handles init script changes)
+VCONTAINER_FORCE_BUILD ?= ""
+python () {
+    if d.getVar('VCONTAINER_FORCE_BUILD') == '1':
+        d.setVarFlag('do_rootfs', 'nostamp', '1')
+}
 
 # Inherit from core-image-minimal for a minimal base
 inherit core-image
diff --git a/recipes-containers/vcontainer/vpdmn-rootfs-image.bb b/recipes-containers/vcontainer/vpdmn-rootfs-image.bb
index 644ce14d..5ca73953 100644
--- a/recipes-containers/vcontainer/vpdmn-rootfs-image.bb
+++ b/recipes-containers/vcontainer/vpdmn-rootfs-image.bb
@@ -24,9 +24,15 @@ LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda
 do_rootfs[file-checksums] += "${THISDIR}/files/vpdmn-init.sh:True"
 do_rootfs[file-checksums] += "${THISDIR}/files/vcontainer-init-common.sh:True"
 
-# Force do_rootfs to always run (no stamp caching)
-# Combined with file-checksums, this ensures init script changes are picked up
-do_rootfs[nostamp] = "1"
+# Force rebuild control:
+# Set VCONTAINER_FORCE_BUILD = "1" in local.conf to disable stamp caching
+# and force rootfs to always rebuild. Useful when debugging dependency issues.
+# Default: use normal stamp caching (file-checksums handles init script changes)
+VCONTAINER_FORCE_BUILD ?= ""
+python () {
+    if d.getVar('VCONTAINER_FORCE_BUILD') == '1':
+        d.setVarFlag('do_rootfs', 'nostamp', '1')
+}
 
 # Inherit from core-image-minimal for a minimal base
 inherit core-image