S7: fix link on_test (#2121)

* S7: fix link on_test

* -ldl only for linux

* Revert "-ldl only for linux"

This reverts commit 6ecc40453a.

* Revert "S7: fix link on_test"

This reverts commit 1ae9ee8740.

* add syslinks for the s7 package

---------

Co-authored-by: 沈浪熊猫儿 <shenda@ustc.edu>

packages/s/s7/xmake.lua

@@ -17,6 +17,10 @@ package("s7")
         end
     end)
 
+    if is_plat("linux") then
+        add_syslinks("pthread", "dl")
+    end
+
     on_install("bsd", "cross", "cygwin", "linux", "macosx", "mingw", "msys", "wasm", "windows", function (package)
         os.cp(path.join(package:scriptdir(), "port", "xmake.lua"), "xmake.lua")
         local configs = {}