[build2] Custom target types for build2

[Boris Kolpackov]

Constantin Runge <c.runge at tum.de> writes:

> do you know if there is a way to define custom target types in
> the build system?

Yes, new target types (and corresponding build rules) can be
defined by build system modules. For an example, see the cli
module which implements a build rule for compiling .cli files
(command line interface definitions[1]) to C++ source code (for
parsing the described command line):

https://github.com/build2/build2/tree/master/build2/cli

Currently such build system modules have to be part of the
build system itself but in a few releases we are planning to
add support for dynamically buildable/loadable modules.

[1] https://codesynthesis.com/projects/cli/