ARROW-18255: [C++] Don't fail cmake check for armv6 (#14611)
ARROW-18255: [C++] Don't fail cmake check for armv6 (#14611)

Authored-by: Yibo Cai <e732a3f0de35687e82bda0008a72e443d2f69704@arm.com>
Signed-off-by: Sutou Kouhei <73218711cdd5d5c30ac66da3cc4d9d9204caf34b@clear-code.com>
apache/arrow,kou/arrow,kou/arrow,apache/arrow,kou/arrow,kou/arrow,apache/arrow,kou/arrow,kou/arrow,apache/arrow,apache/arrow,kou/arrow,kou/arrow,kou/arrow,apache/arrow,apache/arrow,kou/arrow,kou/arrow,apache/arrow,apache/arrow,apache/arrow,kou/arrow,kou/arrow,apache/arrow,kou/arrow,apache/arrow,apache/arrow,apache/arrow