bitbake: cookerdata: Convert multiconfig to use BB_CURRENT_MC

People are struggling with multiconfig as the point the conf file
is injected into the data store is not what people expect. We can't
really use a post config since that is too late and we can't really
use a pre config file since that is too early. In OE terms, we need
something right around the local.conf point so it behaves in a similar
way.

A way to handle this is to set the new variable BB_CURRENT_MC to be the
currently selected multiconfig, then the metadata itself can choose
when to inject the approriate configuration.

(Bitbake rev: 518b9015c2be8d3894277a8e54890d6f04d656c0)

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

bitbake/lib/bb/cookerdata.py

@@ -289,7 +289,7 @@ class CookerDataBuilder(object):
 
             multiconfig = (self.data.getVar("BBMULTICONFIG") or "").split()
             for config in multiconfig:
-                mcdata = self.parseConfigurationFiles(['conf/multiconfig/%s.conf' % config] + self.prefiles, self.postfiles)
+                mcdata = self.parseConfigurationFiles(self.prefiles, self.postfiles, config)
                 bb.event.fire(bb.event.ConfigParsed(), mcdata)
                 self.mcdata[config] = mcdata
 
@@ -305,8 +305,9 @@ class CookerDataBuilder(object):
     def _findLayerConf(self, data):
         return findConfigFile("bblayers.conf", data)
 
-    def parseConfigurationFiles(self, prefiles, postfiles):
+    def parseConfigurationFiles(self, prefiles, postfiles, mc = "default"):
         data = bb.data.createCopy(self.basedata)
+        data.setVar("BB_CURRENT_MC", mc)
 
         # Parse files for loading *before* bitbake.conf and any includes
         for f in prefiles: