Broken link on Build API

[pedropaulosuzuki]

On the manifests page, we link to a Github page that simply states "This specification is obsolete and is not recommended for use anymore. For the previous spec, please see the commit history.", without much more explanation.

[bbhtt]

Not sure why Build API is separately mentioned. Looking at the old specification, this is very similar to autotools and already covered by what simple can do.

[TingPing]

This was well before simple and the point was just to explicitly say what autotools does, in terms of actual commands ran. A lot of project use something autotools-like, so the idea was to specify some common usage.

[bbhtt]

So I guess it is better to remove it then

[TingPing]

I think its useful information but a broken link helps nobody.

[TingPing]

Basically the information:

flatpak-builder modules are broken up into steps:

1. Configure
   This can be meson setup, cmake or ./autogen.sh (controlled by no-autogen and rm-configure) and ./configure plus config-opts

2. Build
   ninja/make plus make-args

3. Install
   ninja/make install (or install-rule) plus make-install-args and controlled by no-make-install.

(There is also a test step but nobody uses this?)