gtk-immodules-cache.bbclass: convert cache creation to postinst_intercept mechanism
This has the following benefits:
- consistent with how the other caches are created into target rootfs
- only runs once per package manager transaction, instead of once per every immodule package
- correctly postpones to first boot if qemu is not working; from postinst itself
this would've required special arrangements to avoid what is now a do_rootfs failure.
Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
