Here's what I use:

nss and nspr are in ~/code/nss and ~/code/nspr respectively.

I export the following:
export USE_64=1
export HOST=localhost
export DOMSUF=localdomain

I occasionally run:
make nss_clean_all && make nss_build_all from the nss directory.  I
hardly ever touch nspr, except to do `hg pull -u`.

I have the following in /etc/hosts
127.0.0.1               localhost.localdomain localhost

That's enough that I can change to ~/code/nss/tests/ssl and run
./ssl.sh without problems.

I also copy a recent file from
tests_results/security/foo.12/ssl_gtests into my home directory.  That
lets me run the attached script, which is very convenient for
debugging.  That gets results in seconds, unlike the scripts, which
take a lot longer just to get through setup steps.

All I need to do is pass part of the name of the test as an argument
(such as "SSLv2ClientHelloTestF") and it runs all the matching tests.
Pass it a -d option and it runs gdb (-r for rr if you have that).