add headeronly to chatscript (#2174)

packages/c/chaiscript/xmake.lua

@@ -1,5 +1,6 @@
 package("chaiscript")
 
+    set_kind("library", {headeronly = true})
     set_homepage("http://chaiscript.com")
     set_description("Header-only C++ embedded scripting language loosely based on ECMA script.")
     set_license("BSD-3-Clause")
@@ -28,4 +29,4 @@ package("chaiscript")
                 double d = chai.eval<double>("function(3, 4.75);");
             }
         ]]}, {configs = {languages = "c++14"}, includes = "chaiscript/chaiscript.hpp"}))
-    end)
+    end)