Fix building on Windows.

	tools/
	* builtin.jam: linking-generator.run (Return nothing
	if it failed).


[SVN r35657]

tools/build

@@ -1 +1 @@
-Subproject commit 622fcf6ed638c7429b872349234e2b307760f4ae
+Subproject commit af6408109b7ec0836dbaafe80b28d192bdd53cda