Add support for SDK tests with LinuxBionic OS type.

Break apart test helpers a bit to make it possible to enable
LinuxBionic in a single test, and add LinuxBionic support to
cc.GatherRequiredDepsForTest.

Test: m nothing
Bug: 160349757
Change-Id: Iace1024c964cee2308c130c945daef9e46c18c66