When plugins DSL is used, there is no need to
manually generate typesafe accessors for extensions and
conventions (by running `./gradlew kotlinDslAccessorsSnapshot`).
* add the way to specify another compatible target for target backend.
It's used to generate a test for X_IR backend even when in a test data
is explicitly written a target: "// TARGET_BACKEND: X".
* Add the ability to run tests "ignored" with the "IGNORE_BACKEND" directive
as regular tests, i.e. w/o catching exceptions.
* Print stack trace of caught exception inside tests "ignored"
with the "IGNORE_BACKEND" directive.
Alexey Tsvetkov