gbuild: GMAKE_OPTIONS overridable ...

[Bjoern Michaelsen]

Hi all,

along with the other changes GMAKE_OPTIONS should now be overrideable from the
environment or the commandline for those daring to try. That means:

 export GMAKE_OPTIONS="-j30 -l9 -sr"
 make

or

 make GMAKE_OPTIONS="-j30 -l9 -sr"

should both allow you to build more optimal on a single (that is no
distcc/icecream) 8-core system by taking in account system load.

Best,

Bjoern