maint: fix issues in syntax-check

maint: fix issues in syntax-check

* cfg.mk (sc_prohibit_colon_redirection): Don't expect `|` to denote
the pipe character in git grep.
(sc_tests_executable)
(sc_case_insensitive_file_names)
(sc_some_programs_must_avoid_exit_failure)
(sc_prohibit_test_background_without_cleanup_)
(sc_prohibit_test_calls_print_ver_with_irrelevant_argument)
(sc_prohibit_test_ulimit_without_require_)
(sc_prohibit_test_background_without_cleanup_)
(sc_THANKS_in_duplicates)
*sc_prohibit_test_calls_print_ver_with_irrelevant_argument):
Don't expect builddir to be a descendant of srcdir.
(sc_strftime_check): Don't check file size against 0 when "N\nq\n" was
already put in the file.
* THANKS.in: Remove me.