pwrap: Avoid dclose(RTLD_NEXT)

In case the libc was not found and RTLD_NEXT is used instead, we should not
dlclose it, otherwise mayhem happens.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

diff --git a/src/priv_wrapper.c b/src/priv_wrapper.c
index acff955..2ca38a0 100644
--- a/src/priv_wrapper.c
+++ b/src/priv_wrapper.c
@@ -727,7 +727,11 @@ void privwrap_constructor(void)
 
 void privwrap_destructor(void)
 {
-	if (privwrap.libc.handle != NULL) {
+	if (privwrap.libc.handle != NULL
+#ifdef RTLD_NEXT
+		&& privwrap.libc.handle != RTLD_NEXT
+#endif
+			) {
 		dlclose(privwrap.libc.handle);
 	}
 }