Fixes the invalid pattern used to test msbuild availability

As discussed in https://github.com/apache/cordova-wp8/pull/12 the
previous pattern was not detecting the msbuid installation in some
localised versions of .net framework. This pattern works with all the
msbuild outputs highlited in that discussion.
Fixes the invalid pattern used to test msbuild availability

As discussed in https://github.com/apache/cordova-wp8/pull/12 the
previous pattern was not detecting the msbuid installation in some
localised versions of .net framework. This pattern works with all the
msbuild outputs highlited in that discussion.
Merge branch 'master' of https://github.com/kScope/cordova-wp8