Fix _socket compilation failures on non-Linux buildbots (cf. issue #1746656).
diff --git a/configure.in b/configure.in
index 52f07e6..3ae9a34 100644
--- a/configure.in
+++ b/configure.in
@@ -1293,7 +1293,7 @@
sys/param.h sys/poll.h sys/select.h sys/sendfile.h sys/socket.h sys/statvfs.h \
sys/stat.h sys/termio.h sys/time.h \
sys/times.h sys/types.h sys/uio.h sys/un.h sys/utsname.h sys/wait.h pty.h \
-libutil.h sys/resource.h netpacket/packet.h sysexits.h bluetooth.h \
+libutil.h sys/resource.h net/if.h netpacket/packet.h sysexits.h bluetooth.h \
bluetooth/bluetooth.h linux/tipc.h spawn.h util.h)
AC_HEADER_DIRENT
AC_HEADER_MAJOR