[gentoo-catalyst] How to enable/disable FEATURES in spec files?

[Matt Turner <mattst88@gmail.com>]

I'm trying to build some new MIPS stages, and need to disable sandbox
from FEATURES due to bug 45814.

I've searched google and the catalyst source but don't see any way to
disable an arbitrary FEATURE flag. I just hacked in a -sandbox and it
works, but I'd like to think there's a better way.

Also, since there are no recent MIPS-N32 stages, I just tar.bz2'd my
installation and put it in the builds/ directory for use as the seed
stage. It uses -march=sb1 in the make.conf, and the packages built by
`catalyst -f file.spec` seem to be using this CFLAG (as shown by the
file command, which reports that the binaries produced are MIPS64,
instead of MIPS IV, as I've requested), even though I've specified
CFLAGS in the spec file, and given it a proper subarch. Spec file is
as follows

---
subarch: mips4_n32
version_stamp: 20100709
target: stage3
rel_type: default
profile: default/linux/mips/10.0/n32
snapshot: 20100907
source_subpath: stage4-mips4_n32-sb1-20100907
cflags: -O2 -march=mips4 -mabi=n32 -mplt -pipe
cxxflags: -O2 -march=mips4 -mabi=n32 -mplt -pipe
ldflags: -Wl,--as-needed

makeopts: -j2
---

What gives? I'm looking at mips.py, and it looks like it should be
assigning CFLAGS given subarch = mips4_n32.

Thanks,
Matt