Weaken multiple main target default build check. Must be identical

rather then only defined on first.

The previous behaviour did not work when there were "default-build" attribute
on project and two alternatives for a main target.

Patch from Michael Stevens.


[SVN r19303]

tools/build

@@ -1 +1 @@
-Subproject commit 5b5bbd0ea47d6954fd92048345e6eea326f4507a
+Subproject commit dce232a6006454e3ad9e7253b690dd6d30a4a253