The custom LibcTest format did not pass litConfig.maxIndividualTestTime
to executeCommand. This caused --timeout to be silently ignored, so
hanging tests like fdiv_test on AMDGPU blocked the entire suite until
the buildbot watchdog killed the process after 1200s.
Added timeout propagation and handling of ExecuteCommandTimeoutException
to return lit.Test.TIMEOUT. This follows the same pattern used by the
GoogleTest format in googletest.py.
cf2b30aa2a