Ivy Foster authored Mar 20, 2015 and Allan McRae committed Mar 26, 2015

We use the get_pkg_arch function with the package name parameter in two places:
1) checking if the package is already built
2) installing build packages

Currently this failed when a package override for "arch" was an array, despite
all our documentation stating that it is indeed an array.  This change makes
these two places fail if there is package override for arch that is not an
array - i.e. of the form arch='i686'.

Signed-off-by: Ivy Foster <joyfulgirl@archlinux.us>
Signed-off-by: Allan McRae <allan@archlinux.org>