Allow Whale generator to be called with several sources, and immediate

return no targets in that case.


[SVN r30542]

tools/build

@@ -1 +1 @@
-Subproject commit d22834b9793c99f500ede8fde7dd56891c270e2e
+Subproject commit 3e3abd45095b522d7012206e049c890e89aaeeaa