cleanup: supress harmless stdout garbage output

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
portage/virtualbox/vmware: hack up make.conf

The default make.conf really doesn't cut it for any kind of
reasonable purpose, so hack it up to contain some stuff that
I want.

Also add vmware- and virtualbox-specific make.conf
customizations.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>