I just tried to build freeglut on Mac OS 10.14 (Mojave) and got the exact same problem. I'm equally stumped on how to fix it. For what it's worth, I was able to install freeglut successfully using MacPorts, but that didn't include the static library that I was hoping for (it does have several .dylib files though). It also came with several .cmake files which might have been useful, but all of my efforts to include them in my project using CMake failed, so I gave up.