BuildSystem: Invoke ldconfig with previous path.

On OpenBSD, gmake uninstall{-all} registered only libraries from /usr/lib and
lost those from /usr/local/lib. Instead, invoke ldconfig on a path.

ASTERISK-27595

Change-Id: I4aa2c0b5e07119d1a556f8ff6349eaf09e986888

Makefile

@@ -972,7 +972,7 @@ ifeq ($(HAVE_DAHDI),1)
 endif
 	$(MAKE) -C sounds uninstall
 ifneq ($(LDCONFIG),)
-	$(LDCONFIG) || :
+	$(LDCONFIG) "$(ASTLIBDIR)/" || :
 endif
 
 uninstall: _uninstall