pgsql: Improve our method for probing the availability of ARM CRCinstr

Improve our method for probing the availability of ARM CRC instructions.

Instead of depending on glibc's getauxval() function, just try to execute
the CRC code, and trap SIGILL if that happens.

Thomas Munro

Discussion: https://postgr.es/m/HE1PR0801MB1323D171938EABC04FFE7FA9E3110@HE1PR0801MB1323.eurprd08.prod.outlook.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1c72ec6f498945eb5981cdedd448aec3977477c8

Modified Files
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configure                         | 45 ++-------------------------------------
configure.in                      | 21 ++----------------
src/include/pg_config.h.in        |  3 ---
src/port/pg_crc32c_armv8_choose.c | 33 +++++++++++++++++++++-------
4 files changed, 29 insertions(+), 73 deletions(-)