Replace the "Add topdir to import path" boilerplate lines in each test
file with a simple "import pmb_test". Use the "# noqa" comment if
"pmb_test" is not used further in the test file, so flake8 does not
complain about an unused module.
Make the path to the testdata available as pmb_test.const.testdata, and
use pmb.config.pmb_src to access the topdir in all tests.
This is in preparation for new "pmbootstrap status" related tests, which
will have shared test code in test/pmb_test/. Also, this makes the
pmbootstrap codebase more consistent with the bpo codebase, which has a
similar "import bpo_test" mechanism.
Install rust (rustc) in native chroot, if it is in the APKBUILD's
build dependencies. Add a test to verify that crossdirect + rust works
as expected.
Closes: #1861
Oliver Smith