It depends on the ecosystem (especially for tools without GUIs, I've found it usually is just two lines at the terminal: one to install the build tool for a given ecosystem and then the other to run it), but sure there are plenty of open source projects which are difficult to build from scratch. However, for most of them this is an acknowledged shortcoming that they try to fix when given the time and resources. It might be a much different world if there was a financial incentive to magnify that shortcoming.