This was my job at Cisco. But it was a C code base, which used nonstandard compiler extensions, and so could not be built without the legacy compilers with their locally made extensions. Also the "unit tests" were actually hardware-in-the-loop tests. And the Makefiles referenced NFS filesystems automounted from global replicas, but none of them were on my continent.

Fun times. Don't work there anymore. Life is good. :)