The rdep check on PKG_BUILD_DIR excludes the ipkg-* staging dirs, but
not the apk-* ones. The package step writes the apk scripts after
.built is touched. If this crosses a second boundary, the next build
sees newer files and packs the package again, which starts the loop
again. The kernel package with its kmods takes several seconds to pack
and is repacked on every build.
Anchor the pattern to PKG_BUILD_DIR, as a plain "*/apk-*" also matches
the build dir of the apk package itself.
Signed-off-by: John Crispin <john@phrozen.org>