If I change the optimization level of the release build to 'None [-O0]' then everything works again. It also works if I set the optimization level to [-Ofast].

This bug is still there as of Xcode 12.5.1... Fix still applies. Would be nice to get this patched into the release builds of Xcode since the default disk name is "Macintosh HD" and the space in that breaks the included build-scripts.

Update: 24 hours and a handful of attempts later, I finally have 12.5.1 successfully installed. Here's hoping something changes by the time 12.5.2 rolls around.

Clearly I'm not the only one experiencing this as most of the recent reviews are about simply downloading/installing Xcode.