This has a couple of advantages over rolling it by hand:
1. it correctly handles include_directories objects, which is always
handy
2. it correctly generates a depfile for you, which makes it more
reliable
3. it requires less typing
we have two functions to do the exact same thing, and they're basically
implemented the same way. Instead, let's just use the BuildTarget one,
as it's more generally available.
Like other language specific modules this module is module for holding
rust specific helpers. This commit adds a test() function, which
simplifies using rust's internal unittest mechanism.
Rust tests are generally placed in the same code files as they are
testing, in contrast to languages like C/C++ and python which generally
place the tests in separate translation units. For meson this is
somewhat problematic from a repetition point of view, as the only
changes are generally adding --test, and possibly some dependencies.
The rustmod.test() method provides a mechanism to remove the repatition:
it takes a rust target, copies it, and then addes the `--test` option,
then creates a Test() target with the `rust` protocol. You can pass
additional dependencies via the `dependencies` keyword. This all makes
for a nice, DRY, test definition.