[TYPO3-english] How to build TYPO3 from Github (or gerrit)

[Urs Braem]

The source from https://github.com/TYPO3/TYPO3.CMS is not the full cms like in the tar on https://typo3.org/download/

I guess this has to be built, right? But how? Composer? 

The reason for my question is that I would like to try out a gerrit patch https://review.typo3.org/#/c/53974/  but I have the same issue there

Thanks for any hint or link!