[pseudo] pseudo env corruption with bash

I thought I'd write down what I've discovered when looking into a
segfault in pseudo on the autobuilder. The bug in question is this one:

https://bugzilla.yoctoproject.org/show_bug.cgi?id=16078

opkg-build is a bash script. The issue is that bash implements its own
setenv/getenv/unsetenv functions which operate on bash variables as
well as environ. What that means is that bash's view is environ+delta.
bash does swap between different environ copies depending on what it is
doing but it only updates that when it is about to exec something that
needs it.

Pseudo noticed problems in this area a while ago and bypassed the bash
wrappers:

https://git.yoctoproject.org/pseudo/commit/?id=80c6334a2e4204cdc7132216f64d1660eed62fd9

The trouble is that glibc's functions alter environ in a way which is
not compatible with bash and the two conflict. Whether there are issues
depends on which variables are set/modified in bash's local delta to
environ.

If I remove the glibc calls and just use bash's wrappers when they are
present, all the valgrind memory errors are removed and things look
much cleaner.

pseudo doesn't access environ directly that I've spotted yet, just via
setenv/getenv.

I'll ponder the right fix a bit more, the hard part will be getting a
list of all the envvars without using environ directly...

Cheers,

Richard