Add pkg-config and version information to every jhbuild module

[dpino]

Moved from #51 (comment)

When pkg-config and version information are present in a jhbuild module, jhbuild will compare the version requested to the version of the library installed via system packages (in case the package was installed). If the system package is newer, then the module is skipped.

Avoiding building modules that are already installed as system libraries will reduce the size of the image. Having pkg-info and version present will also help to inadvertely downgrade a package that is already installed (In case you need to downgrade a package, simply remove the pkg-config or version from the module configuration).

In any case, it seems this mechanism only works in jhbuild for tarballs. I have pushed a merge-request to make the same logic work with git branches:

• Add support for attribute 'version' in Git branches

We have many modules setup as git branches, so we need to get that merge-request merged and jhbuild updated before implementing this change cc @TingPing

[TingPing]

FWIW I don't really see the point of this. We control the versions in the SDK, sans micro version updates by Ubuntu. So we just remove any modules we don't need whenever.

[dpino]

FWIW I don't really see the point of this. We control the versions in the SDK, sans micro version updates by Ubuntu. So we just remove any modules we don't need whenever.

The meson module was part of the JHBuild moduleset for a long time even though it was not necessary (#37). The same is currently happening with the openh264 module, as I explained in #51 (comment).

IMHO, the best way to inadvertely downgrading a module via JHBuild, or installing a module that it's not necessary, is to attach the pkg-config information to every module (whenever possible). It may also help to save time in the build of the JHBuild modules and save space in the image.