Compile error on the aarch64 platform: Missing asm/hwcap.h

Hi,

Compile error on CentOS Linux release 7.6.1810 (AltArch) with the message
“‘HWCAP_CRC32’ undeclared”.

Relevant code from discussion:
https://www.postgresql.org/message-id/4496616.iHFcN1HehY%40portable-bastien
It mentions: "It doesn't look like I need to include <asm/hwcap.h> from
Bastien's
original message, because <sys/auxv.h> pulls in <bits/hwcap.h>
already."

However, the bits/hwcap.h file included with glibc in CentOS 7.6 lacks
these symbol definitions (the file is nearly empty). This file appears to
be an internal glibc dependency, so it's preferable to directly use
asm/hwcap.h for the required symbol definitions.

After modifying the code to add `include <asm/hwcap.h>`, the compilation
succeeded.

--
GaoZengqi
pgf00a(at)gmail(dot)com
zengqigao(at)gmail(dot)com