Add `--gtest_shard_index` and `--gtest_total_shards` command line arguments.HEADmain

This uses the environment variables as the default value for the command line argument, so this is not a breaking change to most reasonable existing use cases. This *is* a breaking change if a process expects changes to the sharding environment variables to be visible after parsing the command line arguments.

The motivation for this is that some environments do not support environment variables, which prevents the usage of test sharding. These environments also run on simulators and other slow hardware, where sharding is especially important. I've tried a few other things, like hacking together a fake implementation of `getenv`/`setenv`, but this is a pretty unreliable approach on the platform in question.

This also seems like an improvement in consistency to me. Currently, other test selection mechanisms (e.g. filtering, shuffling, repeat), `use arguments (or at least have command line arguments as an option), while as far as I can tell, sharding is the only mechanism which can *only* be specified with environment variables.

PiperOrigin-RevId: 892324928
Change-Id: I5cf814e46e16072e7c160e54c426b02300fe712b

0 files changed, 0 insertions, 0 deletions