Add builddepends metadata field to recipes

[matteodelabre]

(As proposed by @Eeems on Discord.)

Some recipes require specific packages that are not provided by the Toltec Docker images. Currently, these are calculator and plato. We should add a builddepends field, similar to Arch’s makedepends, which contain be a list of Debian packages required for the build() function.

[Eeems]

Preferably it would also cache the image with the builddeps installed after the first run so that subsequent builds don't need to reinstall them.

[matteodelabre]

I’m starting to implement this. To make things simpler, I’ll omit the optdepends and checkdepends fields from Arch’s PKGBUILDs, which could still be implemented at a later time.

• Specifying dependencies. The depends and makedepends fields will support entries of the form: type:name<=>version, where
  • type is one of apt (for installing dependencies from Debian, can only be specified in the makedepends field) or opkg (for installing dependencies from Entware or Toltec),
  • name is the package name to install,
  • <=> is an optional version comparator from <, <=, =, => or >,
  • version is an optional version constraint.
• Building packages. Before invoking the prepare() and build() functions, the build script will make sure that all the required Debian, Entware and Toltec packages are installed in the Docker container’s $SYSROOT directory. If a required Toltec package is not yet available, the build of that package is triggered first.
• Support for split packages. Only dependencies declared at the top-level of a split package recipe will be enforced before starting the build. A split recipe cannot declare a top-level makedepends on one of the packages it generates.

[matteodelabre]

Also, regarding #170 (comment), I’m thinking that the prepare() function should be moved to run inside the Docker container. Thoughts?

[Eeems]

Perhaps, this will allow us to have access to more tools out of the gate.