As it is right now, NSS cannot be built statically. There is some work in progress in bug 534471 and bug 533014 (NSS and NSPR respectively) but these patches are quite old and likely don't apply any more. It seems that nobody at Mozilla is currently working on this.
As to Chromium, they are using a heavily patched NSS version. Also, they are using GYP to build NSS, not the Makefiles normally supplied with NSS. You could probably build their NSS version but I'm not sure whether it is really useful outside Chrome. The relevant directories are deps/third_party/nss/ and src/net/third_party/nss/, former being NSS without libssl and the latter being libssl only.