t5608: mark >4GB tests as EXPENSIVE
Even with precomputed pack constants that reduced the helper's runtime from minutes to seconds, the >4GB clone tests still take 200-850 seconds across CI jobs. The bottleneck is no longer the pack generation but the clone operations themselves: transporting, unpacking, and indexing 4 GiB of data through unpack-objects and index-pack is inherently expensive. As Jeff King pointed out [1], t5608 alone takes 160 seconds on his laptop while the rest of the entire test suite finishes in under 90 seconds, and the test's disk footprint (4+ GiB source repo, then two clones) is problematic for developers who use RAM disks for their trash directories. Gate the >4GB tests on the EXPENSIVE prereq (which requires GIT_TEST_LONG to be set) in addition to SIZE_T_IS_64BIT, keeping them out of normal local test runs. [1] https://lore.kernel.org/git/20260501063805.GA2038915@coredump.intra.peff.net/ Assisted-by: Claude Opus 4.6 Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>