Tests can't run in parallel due to collisions on this directory:

https://github.com/flutter/engine/blob/main/impeller/compiler/compiler_test.cc#L13

These are part of impeller_unittests, which would be helpful to run with gtest-parallel. Otherwise impeller_unittests is likely too slow to run in unopt with asan etc. enabled.