Fix #624: Provide ASV-specific environment variables to subprocesses
Fix #624: Provide ASV-specific environment variables to subprocesses

This follows a general pattern in development and integration tools.

spacetelescope/asv,pv/asv,airspeed-velocity/asv,pv/asv,spacetelescope/asv,spacetelescope/asv,airspeed-velocity/asv,qwhelan/asv,qwhelan/asv,airspeed-velocity/asv,pv/asv,qwhelan/asv,pv/asv,spacetelescope/asv,airspeed-velocity/asv,qwhelan/asv