I used to work in a project around 2000 that would take 1h build time per architecture/OS combination.

Doing a full build across HP-UX, Aix, Solaris, Red-Hat Linux and Windows for 32 and 64 bits took almost a full day.

EDIT: It was a mix of C and TCL

Yep. A while ago I found myself needing to recompile the Linux kernel for Android, and I was amazed at how fast the build was (I think I last built a kernel in the 90s). It took a lot less time than it takes Android to start up!