gold: Skip some incremental tests

Skip incremental_test_2, incremental_test_3, incremental_test_4,
incremental_test_5, incremental_copy_test, incremental_common_test_1
and incremental_comdat_test_1 when -fcf-protection is used to compile
gold since gold doesn't properly support -fcf-protection on Intel CET
enabled OS.

Also skip incremental_copy_test and incremental_comdat_test_1 for GCC 9
or later since they failed with GCC 9 or later.

	PR gold/23539
	* configure.ac: Check for GCC 9 or later and for -fcf-protection.
	* configure: Regenerated.
	* testsuite/Makefile.am (check_PROGRAMS): Skip incremental_test_2,
	incremental_test_3, incremental_test_4, incremental_test_5,
	incremental_copy_test, incremental_common_test_1 and
	incremental_comdat_test_1 for -fcf-protection.  Also Skip
	incremental_copy_test and incremental_comdat_test_1 for GCC 9 or
	later.
	* testsuite/Makefile.in: Regenerated.