tests: Work on more thorough error handling

tests/args.c

tests/resource/getrusage.c

tests/unistd/brk.c

tests/unistd/chdir.c

tests/unistd/exec.c

tests/unistd/fchdir.c

tests/unistd/fsync.c

tests/unistd/ftruncate.c

tests/unistd/getcwd.c

tests/unistd/gethostname.c

tests/unistd/isatty.c