stallDumpDirectory function
The dump root: stallDumpDirectoryOverride, then FA_TRIAL_DIR, then
<systemTemp>/stall-dumps.
Implementation
Directory stallDumpDirectory() {
final override = stallDumpDirectoryOverride;
if (override != null && override.isNotEmpty) return Directory(override);
final lookup = providerStackEnvLookup;
final env = lookup == null ? null : lookup(stallDumpDirEnvVar);
if (env != null && env.isNotEmpty) return Directory(env);
return Directory.systemTemp.createTempSync('fa-stall-root');
}