src/arch/aarch64: fix uclibc build

Fix the following build failure with uclibc-ng raised since version 2.3
and
https://github.com/axboe/liburing/commit/c6bc86e2125bcd6fa10ff2b128cd86486acadff6:

In file included from lib.h:12,
                 from setup.c:4:
arch/aarch64/lib.h:7:10: fatal error: sys/auxv.h: No such file or directory
    7 | #include <sys/auxv.h>
      |          ^~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/cc44d714c9267dd7a98debeb8c81c4ee1efe4ebb

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
1 file changed