s390x: Enable nptl for s390x

S390x user emulation can do nptl. Reflect this in the configure script.

Signed-off-by: Ulrich Hecht <uli@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/configure b/configure
index 2ef5c75..e91525f 100755
--- a/configure
+++ b/configure
@@ -3150,6 +3150,7 @@
     target_phys_bits=64
   ;;
   s390x)
+    target_nptl="yes"
     target_phys_bits=64
   ;;
   *)