populate_sdk_base: add dependency of do_package_write_* tasks
nativesdk packages were created only for the first backend listed in
PACKAGE_CLASSES. Hence, if one had it set to "package_rpm package_ipk"
and did a 'bitbake -c populate_sdk core-image-something', the nativesdk
packages were created only for rpm.
This is particularily bad for adt-installer which is based on opkg
repos.
Credits go to richard.purdie@linuxfoundation.org who suggested me this
fix.
[YOCTO #5900]
Signed-off-by: Laurentiu Palcu <laurentiu.palcu@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
