asterisk: do postgresql hackery only if postgresql is installed

network/asterisk/asterisk.conf

@@ -2,6 +2,7 @@
 # This copyright note is auto-generated by ./scripts/Create-CopyPatch.
 #
 # Filename: package/.../asterisk/asterisk.conf
+# Copyright (C) 2009 The OpenSDE Project
 # Copyright (C) 2004 - 2006 The T2 SDE Project
 # Copyright (C) 1998 - 2004 Clifford Wolf
 #
@@ -33,5 +34,7 @@ makeinstopt="$makeopt install"
 
 var_append makeinstopt " " "samples"
 
+if pkginstalled postgresql; then
 	var_append GCC_WRAPPER_INSERT " " "-I/opt/postgresql/include"
 	var_append GCC_WRAPPER_INSERT " " "-L/opt/postgresql/lib"
+fi