Handle the <library> property in the linking-generator, not in

lib-target-class and exe-target-class. This makes the 'unit-test' rule
work with <library>.


[SVN r25768]

tools/build

@@ -1 +1 @@
-Subproject commit 18b96d9ce757eb8648fb2d46750d2da39ef40288
+Subproject commit 543fb2d180b80292af58ae570a5db5e3c96fa4b6