NSS libraries are missing from mar-tools archive

While testing mar file generation on Linux, Kathy and I discovered that the signmar program from mar-tools-linux64.zip will not start. The error message displayed is: ERROR: Could not initialize NSS Trying to run certutil produces a more informative error message: certutil: function failed: PR_LOAD_LIBRARY_ERROR: Failure to load dynamic library libsoftokn3.so: cannot open shared object file: No such file or directory

I think we probably need libfreebl3.so as well.

Why were those two libraries removed from NSS_LIBS in gitian-firefox.yml as part of legacy/trac#21239 (moved)? Are they not built at all, or maybe they are in a different location in ESR52?