multilib: fix SSTATE_ARCHS for multilib usage

When building multilibs, we need to inject the multilib sstate pkgarch
into SSTATE_ARCHS so the list forms a complete search path. Add a tweak
to do this.

PACKAGE_ARCH defaults to TUNE_PKGARCH so this is equivalent and just
guards against recipes changing the value which may have other unwanted
side effects.

(From OE-Core rev: 37126ffc7ccbd3df57ebbd8e581d158f03bb3b4c)

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

meta/classes/multilib.bbclass

@@ -30,6 +30,9 @@ python multilib_virtclass_handler () {
         if val:
             e.data.setVar(name + "_MULTILIB_ORIGINAL", val)
 
+    # We nearly don't need this but dependencies on NON_MULTILIB_RECIPES don't work without it
+    d.setVar("SSTATE_ARCHS_TUNEPKG", "${@all_multilib_tune_values(d, 'TUNE_PKGARCH')}")
+
     overrides = e.data.getVar("OVERRIDES", False)
     pn = e.data.getVar("PN", False)
     overrides = overrides.replace("pn-${PN}", "pn-${PN}:pn-" + pn)