In preparation for switching from merge-recursive to merge-ort as the default strategy, have the testsuite default to running with merge-ort. Keep coverage of the recursive backend by having the linux-gcc job run with it. Signed-off-by: Elijah Newren <newren@gmail.com> Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>