aa85dcf472 build: sync ax_boost_chrono/unit_test (fanquake) Pull request description: [ax_boost_chrono](https://github.com/bitcoin/bitcoin/blob/master/build-aux/m4/ax_boost_chrono.m4) and [ax_boost_unit_test_framework](https://github.com/bitcoin/bitcoin/blob/master/build-aux/m4/ax_boost_unit_test_framework.m4) were updated from upstream in #12678. However some minor upstream changes were missed. Pull those changes in here so these files actually reflect their upstream serial. Tree-SHA512: 71d9ee7a1616d9d36e6f63dedb6687918c3662bde724cdda1fdf3eb039c8973acd166273876a9b2671a7e087149fcf956552f9f2b946e5ee1835d12944c0065d
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