liblog: statically link tests

Some liblog tests test symbols that aren't otherwise used on the
platform.  Statically link the tests such that we can add version
scripts that expose only the symbols used by the platform, and still
allow the tests to test the rest.

Test: build + unit tests
Change-Id: I898280fa52d31a2c7ad4eafdaa85e8b5f2e87971