Don't create Python bytecode files during interpreter discovery

[akx]

Summary

As @konstin noted, python -I ignores PYTHONDONTWRITEBYTECODE, so --no-compile-bytecode may end up with bytecode spilled onto the disk nevertheless.

This should fix that by way of adding -B.

Test Plan

None so far. I can add proper tests if required, if this is deemed a good idea :)

Closes #7696.

[zanieb]

Seems reasonable to me if @konstin signs off.

[konstin]

We have test coverage through the general ecosystem and python discovery tests, i don't think we need specific tests that we are not writing bytecode.

For performance considerations: We're caching interpreter discovery, so this code should run only once, so the lack for writing bytecode should not matter. If this should turn out to affect could start times of containers, we should extend --compile to also bytecode compile the standard library, if permissions allow.