Depending on glfw and dawn_utils at the same time would cause two occurrences of libglfw.a in the linker command line, and this would violate the one definition rule on macOS. (But Windows and Linux builds are not affected because the error only happens when -Wl,-ObjC is specified)
Depending on dawn_utils would trigger the build of GLFW, which is something we want to gradually get rid of (#100)
dawn_utils is not emulated by Emscripten, so building it from source will trigger the full build of Dawn and GLFW, which is not yet possible.
-Wl,-ObjCis specified)