Here are the required patches for compiling dev-libs/nss-3.8 on amd64. I didn't write this myself, just pulled the needed parts from the amd64 patch for mozilla-1.4.
Created attachment 20191 [details, diff] patch against the nss ebuild
Created attachment 20192 [details, diff] patch against the nss source
I support this patch. Works for me.
works, thanks, done