A while ago I followed the coursera compilers course that used COOL but I was interested in writing a compiler that could run on windows too, didn't use a parser generator, and compiled to a native executable instead of using a MIPS emulator. So I wrote a new COOL compiler without using any skeleton code from a course. The compiler supports windows and linux.

If you're using LLVM for a project you might learn some tricks here. Especially if you're targeting windows, some things like generating the correct linker command and supporting both 32 and 64 bit are tricky.