There appears to be a missing link library. The error message is

/usr/bin/ld: CMakeFiles/gmsh.dir/Fltk/FlGui.cpp.o: undefined reference to symbol 'XCreateBitmapFromData'
//usr/lib64/libX11.so.6: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status

I have to manually add -lX11 to the link libraries. I'm using Fedora 28.