This ensures that each repository's "npm test" command is fully
independent of wherever it might be in the filesystem.
Bug: T206485
Change-Id: I5ec93fff138f9821e151b28f6ecd9f891e4912c6
'mw' are '$' are globals, always have been, and aren't going
anywhere. They're every bit as real as their longer versions.
If anything, the longer ones are less "real" or 'stable" because
they're not used internally by RL and easier to accidentally
replace or override. For anecdotes and history, see 91f950d6b0.
Change-Id: I526fb8c961d9477992d88f2780a0ff4cbdc51923
