useradd: Handle users from a package being used in others

useradd: Handle users from a package being used in others

If there is a package A (TUNE_PKGARCH) which is depended upon by B which
is MACHINE_ARCH and you build B for machine X, then Y, the user isn't
present in the sysroot for machine Y since the useradd code is never
triggered.

The change ensures the code does get triggered and the user is present.

[YOCTO 4739]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>