BUT, both options are not good, as they are stopping me from even running initdb.
The easiest path for testing will be to use an unpatched PostgreSQL to `initdb` and create a new database. Then start up a patched one that simply skips WAL writing against an already-`initdb`'d data directory.
You probably won't be able to safely restart PostgreSQL, but all you're doing is performance analsys so one-shot operation on a throw-away data directory is probably fine.