$NetBSD: patch-configure.ac,v 1.1 2022/04/12 22:22:26 nikita Exp $

Upstream commit 1acaf9980b55ae180cc08db218b9face28202519
from Alyssa Ross.

Use popcount64 from libc when available

Without this, we get a compiler error on NetBSD because the one in
libc has a slightly different prototype.

libcpuid_util.c:78:12: error: conflicting types for 'popcount64'
   78 | static int popcount64(uint64_t mask)
      |            ^~~~~~~~~~
In file included from /nix/store/155rj8nqh3xd80vpa8hl35p3hk7pacys-include-netbsd-8.0/include/string.h:98,
                 from libcpuid_util.c:30:
/nix/store/155rj8nqh3xd80vpa8hl35p3hk7pacys-include-netbsd-8.0/include/strings.h:61:14: note: previous declaration of 'popcount64' was here
   61 | unsigned int popcount64(__uint64_t) __constfunc;
      |              ^~~~~~~~~~

* Return unsigned int from popcount64

Matches NetBSD libc, where popcount64 originates.

--- configure.ac.orig
+++ configure.ac
@@ -43,6 +43,8 @@ LT_INIT
 AM_CPPFLAGS="$CPPFLAGS"
 
 AC_CHECK_HEADERS([stdint.h])
+AC_CHECK_FUNCS([popcount64])
+
 AC_CHECK_PROGS([DOXYGEN], [doxygen])
 AM_CONDITIONAL([HAVE_DOXYGEN], [test -n "$DOXYGEN"])