pgsql: Fix pg_popcount_aarch64.c to build with ancient glibc releases.

Fix pg_popcount_aarch64.c to build with ancient glibc releases.

Like commit 6d969ca68, except here we are mopping up after 519338ace.
(There are no other uses of <sys/auxv.h> in the tree, so we should
be done now.)

Reported-by: GaoZengqi <pgf00a@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: /messages/by-id/CAFmBtr3Av62-jBzdhFkDHXJF9vQmNtSnH2upwODjnRcsgdTytw@mail.gmail.com
Backpatch-through: 18

Branch
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REL_18_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/6a51707551270eb2d17ed53c4256cc89299fa3b7

Modified Files
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src/port/pg_popcount_aarch64.c | 4 ++++
1 file changed, 4 insertions(+)