cooker: Fix priority for virtual recipes

[Richard Purdie <richard.purdie@linuxfoundation.org>]

When making filename comparisons for recipes for priority calculations,
we need to split off any virtual prefix. Without this, BBCLASSEXTEND
version of recipes don't follow the priority settings they should.

[YOCTO #2933]

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

diff --git a/bitbake/lib/bb/cooker.py b/bitbake/lib/bb/cooker.py
index 1b3bb84..4861212 100644
--- a/bitbake/lib/bb/cooker.py
+++ b/bitbake/lib/bb/cooker.py
@@ -642,7 +642,8 @@ class BBCooker:
         # Calculate priorities for each file
         matched = set()
         for p in self.status.pkg_fn:
-            self.status.bbfile_priority[p] = self.calc_bbfile_priority(p, matched)
+            realfn, cls = bb.cache.Cache.virtualfn2realfn(p)
+            self.status.bbfile_priority[p] = self.calc_bbfile_priority(realfn, matched)
  
         # Don't show the warning if the BBFILE_PATTERN did match .bbappend files
         unmatched = set()