asymptote: changed to use boehm-gc when installed

graphic/asymptote/asymptote.conf

@@ -2,7 +2,7 @@
 # This copyright note is auto-generated by ./scripts/Create-CopyPatch.
 #
 # Filename: package/.../asymptote/asymptote.conf
-# Copyright (C) 2004 - 2006 The T2 SDE Project
+# Copyright (C) 2009 The OpenSDE Project
 #
 # More information can be found in the files COPYING and README.
 #
@@ -12,6 +12,8 @@
 # GNU General Public License can be found in the file COPYING.
 # --- SDE-COPYRIGHT-NOTE-END ---
 
-# disable garbage collecting - TODO: patch it to compile with
-# var_append confopt ' ' "--enable-gc=system"
-var_append confopt ' ' "--disable-gc"
+if pkginstalled boehm-gc; then
+	var_append confopt ' ' "--enable-gc=system"
+else
+	var_append confopt ' ' "--disable-gc"
+fi