[merge from head] Fix RC tool to fallback to the null rc type when a real one can't be found.

[SVN r33700]

tools/build

@@ -1 +1 @@
-Subproject commit da2651fc471d38fac1b6505f6fb70c1d45a18016
+Subproject commit 7f2e9731876dcf116a5e2afcac791697217ed75e