Add <toolset>msvc as optional property for msvc.compile* generators,

otherwise, only RC->OBJ is tried when OBJ target is needed.


[SVN r23279]

tools/build

@@ -1 +1 @@
-Subproject commit 8c7ea9b33028a8ceb17b082c3a51614bb4a06807
+Subproject commit 1e560a18e086351cd2d1b75168bbe5b703f9bf4d