std.build.RunStep: clean up some leftover mess

* Remove some functions that are no longer needed since
   EmulateableRunStep is gone.
 * Add removeEnvironmentVariable function.
 * Support printing environment variables in --verbose mode.
a0dd2919ebAndrew Kelley committed on 3/15/2023, 5:48:14 PMparent61d7e31
2 files changedLine totals unavailable