Document Makefile dependencies

[silverwind]

Description

The Makefile has various dependencies on command line tools which should be documented as a requirement for developing Gitea. I'm thinking this should be in a file in the repository itself and not on the website, maybe in CONTRIBUTING.md or README.md.

[lafriks]

I think CONTRIBUTING.md would be best place for this

[bkcsoft]

@silverwind Do you have a list of those? If you're referring to various go get then those should be fetched automagically if they don't exist

[sapk]

Looking quickly at makefile most (every ?) of deps are go project that are go get. (gocovmerge is used but not go get, we should fix this). But we could still list them in CONTRIBUTING.md at least to give credits and explain for what we use them.

[sapk]

And looking at #2194 ref. I think this PR is mostly for inkscape/convert/... new deps.

[lafriks]

@sapk not only, for development there is also make and golang dependency ;)

[silverwind]

I think these are all that are not pulled via go get:

git, gocovmerge, lessc, inkscape, ImageMagick, zopflipng

Can gocovmerge be installed via go get, by the way?

[sapk]

I have done a PR to fix gocovmerge. Lessc is based on a go version that is go get.