Try filter, del_files doesn't work (#291)

packages/c/cef/port/xmake.lua

@@ -1,8 +1,7 @@
 add_rules("mode.release", "mode.debug")
 target("cef")
     set_kind("static")
-    add_files("libcef_dll/**.cc")
-    del_files("libcef_dll/ctocpp/test/**")
+    add_files("libcef_dll/**.cc|ctocpp/test/**.cc")
     add_includedirs(".")
     add_headerfiles("include/(**.h)")
     add_defines("WRAPPING_CEF_SHARED")