pkg_comp mysteriously overwrites sandbox' mk.conf

[Mayuresh <mayuresh%acm.org@localhost>]

I am completely new to pkg_comp

So far I have succeeded in building using sandbox shell. I get the
familiar pkgsrc environment with the shell.

However if I try to run bulk bulds without using the sandbox shell (using
pkg_comp commands) the builds are failing in cwrappers.

The logs suggest that MAKE_JOBS should be explicitly defined.

I do not see the contents of extra.mk.conf getting copied to mk.conf in
the sandbox.

Moreover, if I manually place some settings in the sandbox' mk.conf, when
I run a pkg_comp command they are getting overwritten to a default
mk.conf, in which MAKE_JOBS is absent, which fails the build.

Any suggestions from experienced pkg_comp users would be of great help.

-- 
Mayuresh