improve pcre2

packages/p/pcre2/xmake.lua

@@ -14,10 +14,8 @@ package("pcre2")
         add_deps("cmake")
     end
 
-    on_load(function (package)
-        package:addvar("links", "pcre2-8")
-        package:addvar("defines", "PCRE2_CODE_UNIT_WIDTH=8")
-    end)
+    add_links("pcre2-8")
+    add_defines("PCRE2_CODE_UNIT_WIDTH=8")
 
     if is_plat("windows") and winos.version():gt("winxp") then
         on_install("windows", function (package)