Make bdist_* commands respect --skip-build passed to bdist (#10946).

There was already a test for this, but it was complicated and had a
subtle bug (custom command objects need to be put in dist.command_obj so
that other command objects may see them) that rendered it moot.
diff --git a/Misc/NEWS b/Misc/NEWS
index 5106f1f..d08d94e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -269,7 +269,8 @@
 -------
 
 - Issue #10946: The distutils commands bdist_dumb, bdist_wininst and bdist_msi
-  now respect a --skip-build option given to bdist.
+  now respect a --skip-build option given to bdist.  The packaging commands
+  were fixed too.
 
 - Issue #12287: Fix a stack corruption in ossaudiodev module when the FD is
   greater than FD_SETSIZE.