The tests don't work when reading/writing to file descriptors in the
sandbox after entering capability mode (and wouldn't have, regardless
of the framework), so adjust the tests so they function within the
framework.
For tests that enter capability mode over the course of the test, the
following is now done:
1. Fork child process for capability mode test.
2. In child...
i. Enter capability mode.
ii. Test invariants.
iii. Exit after calling test function.
3. Collect status for child and determine whether or not it completed
successfully.
In order to test the invariants in the child process, they now use assert(3)
instead of ATF_REQUIRE*, as the atf-c-api functions right to results files
in the directories in order to determine where and how tests fail.
While in the area, fix several -Wshadow and -Wunused warnings found when I
bumped WARNS up to 6, and fix some minor style(9) issues with indentation
and type alignment.
PR: 215690
7f9785e873