[yocto] setting arch of a single package of a recipe

[Joshua DeWeese]

Is it possible, when splitting a recipe into multiple packages, to
change the arch of only one package? (example: setting foopackage-doc
arch to "all") I can't seem to find a way to set PACKAGE_ARCH for a
single package.

I've tried PACKAGE_ARCH_${PN}-doc which didn't work. Grepping for
"PACKAGE_ARCH_" seems to indicate overriding is possible for machine
names at least.

-Josh