build: always nuke apks_* cache to prevent stale package errors

Stale apks_* dirs (from old mirror or previous version pin) cause
"unable to select package" failures. Nuke them on every build.
kernel_*, syslinux_*, grub_* are still preserved — they're large,
stable, and only need to change when KERNEL_PKG_VERSION changes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/builder/build.sh

@@ -181,11 +181,11 @@ cp "${BUILDER_DIR}/genapkovl-bee.sh" "${HOME}/.mkimage/"
 # Export overlay dir so the profile script can find it regardless of SRCDIR.
 export BEE_OVERLAY_DIR="${OVERLAY_DIR}"
 
-# Clean workdir selectively: remove everything except apks cache so packages aren't re-downloaded.
-# mkimage stores each section in a hash-named subdir; apks_* dirs contain downloaded packages.
+# Clean workdir: always nuke apks_* (stale packages from old mirror/version cause "unable to select" errors).
+# Keep kernel_*, syslinux_*, grub_* — these are large but stable; they only change when KERNEL_PKG_VERSION changes.
 if [ -d /var/tmp/bee-iso-work ]; then
     find /var/tmp/bee-iso-work -maxdepth 1 -mindepth 1 \
-        -not -name 'apks_*' -not -name 'kernel_*' \
+        -not -name 'kernel_*' \
         -not -name 'syslinux_*' -not -name 'grub_*' \
         -exec rm -rf {} + 2>/dev/null || true
 fi