staging/allarch: Remove hardcoded PACKAGE_ARCHS from the class
The code was making an assumption that the only PACKAGE_ARCH in use
was TUNE_PKGARCH. This is incorrect so iterate over the list from
PACKAGE_EXTRA_ARCH instead.
We also need to change allarch to preserve this variable, else the
staging code doesn't function. We do this in a way which clears the
variable history so that the task hashes remain unaffected.
[Thanks to Andrew Goodbody <andrew.goodbody@cambrionix.com> for
testing/fixing]
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
