> Which var is the preference? I'm using .MAKEFLAGS since that seems to be
> the one that the docs imply is where new env vars go you want passed along.

Actually given the way its implemented, .MAKEOVERRIDES is probably best.
You are then closer to mimicking what would happen if you'd done

$ make TOP=/foo

when Var_Set is called for VAR_CMD variables, the variable name is
appended to .MAKEOVERRIDES and that's how it eventually ends up in the
child's $MAKEFLAGS.

--sjg