fuzz: try setting PYTHONNOUSERSITE=1 to avoid loading site-packages
Right now the fuzzer is crashing trying to look up the home dir for
uid 0, which is breaking in the fuzz environment.
Differential Revision: https://phab.mercurial-scm.org/D4936
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}