Flaky avocado tests, gdbstub and gitlab tweaks - gdbstub, properly halt when QEMU is having IO issues - convert skipIf(GITLAB_CI) to skipUnless(QEMU_TEST_FLAKY_TESTS) - drop mips malta cpio test as assets expire in Debian archive - tag sbsa-ref tests as TCG only - build the correct microblaze for avocado-system-ubuntu - add optional flaky tests job to CI