After some Googling, it seems that version problems may have been more central than I'd recalled. Xcode is free and includes command-line tools, but looking at it brings up vague memories of incompatibility with my OS at the time. The Apple developer website allows direct download of those tools but also requires a paid signup. And apparently trying to invoke gcc or the like from the command line should have brought up an update option, but that definitely didn't happen. Perhaps it wasn't an option in an OS build as old as mine, although it wouldn't have been older than 2009 or 2010. (I eventually just threw up my hands and installed an Ubuntu virt through Parallels.)

So, probably less severe than I'd thought, but the basic problem remains: violating Apple's assumptions is a bit like being a gazelle wending your way back to a familiar watering hole only to get splattered by a Hummer howling down the six-lane highway that's since been built in front of it.