[aur-general] optional dependencies that require explicit installation

[Michael Schubert]

Hi,

I'm trying to make a PKGBUILD for a scientific library (libsbml). It has
bindings for C/C++ that are installed by default and for a variety of other
languages on demand. I'm not quite sure about the proper way to handle this:

- for a language binding to be built, the package (e.g. python, perl, ruby,
etc.) need to be installed and they need to be enabled in cmake using the
-DWITH option
- if a language binding is build, I need to set the path as well (because it
is somewhere nonstandard by default)

So, in order for this to work:

- how should I check if a package is installed? I found no if-available
option in the cmake scripts; pacman -Q would be an option (the best one?),
or checking for the existance of a specific file (probably not so good)
- if I'd like to separate build() and package() routines, is there a way of
getting around adding each binding as a variable in global scope?- that does
not seem like an optimal solution given the other packaging standards

Thank you for any advice.
Michael