Principia requires a library that's not available?

[Zeiss Ikon]

I've found Principia Fibonacci for 1.7.3, running on Ubuntu 16.04.3 LTS, won't start; it gives "unknown error" and talks about the working directory needing to be in the <ksp directory> and needing version 6.0-2 of libraries libc++ and libc++abi.

Problem is, both of those libraries are at version 3.7 in Ubuntu 16.04.  It appears that even though I'm using a still-supported version of Ubuntu, I'll have to "upgrade" (it's not really an upgrade, it's "install everything clean") in order to be able to use current versions of Principia.  is that correct, or does someone know a way to use libc++ and libc++abi 6.0-2 in my version of Ubuntu?