tests/frontend: Refactor tests for default targets
tests/frontend/buildcheckout.py
is already very crowded with all sorts
of tests. Since this test is not really about testing bst build
but
rather about testing whether BuildStream can detect the default targets
correctly, move it to a separate test module.
At the same time, also improve the actual tests. Currently the test compares the number of sub-directories in BuildStream log directory with the number of elements. Change it such that we directly query BuildStream about what's been built rather than trying to guess.
While doing so, sanitize its project directory to make it clearer what's being tested.
Edited by Chandan Singh