Minor change to PhutilInfrastructureTestCase::testLibraryMap

Summary: Modify PhutilInfrastructureTestCase::testLibraryMap to use phutil_get_current_library_name() instead of hard-coding the library name.

Test Plan: Ran arc unit, tests passed. Added a new function without running arc liberate, tests failed.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9844