improve tests

Author: waruqi

tests/projects/csharp/console_with_runtime_json/src/Program.cs

@@ -1,6 +1,6 @@
 using System.Text.Json;
 
-var runtimeFile = Path.Combine(AppContext.BaseDirectory, "runtime.json");
+var runtimeFile = Path.Combine(Directory.GetCurrentDirectory(), "runtime.json");
 if (!File.Exists(runtimeFile)) {
     Console.WriteLine("runtime.json missing");
     return;

tests/projects/csharp/console_with_runtime_json/xmake.lua

@@ -4,3 +4,4 @@ target("app")
     set_kind("binary")
     add_rules("csharp")
     add_files("src/Program.cs")
+    set_rundir("src")