Jumbo Makfiles update.

Jumbo Makfiles update.

- eliminate ambiguities between GNU-ish and SysV-ish make flavors;
- switch [back] to -e;
- fold/unify rules;

This is follow-up to the patch introducing common BUILDENV. Idea is
to collect as much parameters in $(TOP) as possible and "strip" lower
Makefiles for most variables [and thus makes them more readable].