For historical reasons Meson supports only a single cross configuration file but
multiple native configuration files. Add support for multiple cross files, so
that recipes such as glib can use the toolchain cross file and extend it with a
recipe-specific cross file containing values needed to build.
Signed-off-by: Ross Burton <ross.burton@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
