Upstream googletest prints "Running main() from gtest_main.cc" to stdout prior
to running tests. LLVM removed that print statement in r61540. If a user were
to use lit to run tests that use upstream googletest, however, lit
reports "Running main()" as an invalid test name.
To avoid such a failure, add an extra conditional to formats/googletest.py.
Also add tests to demonstrate the modified behavior.