Made src subfolders detection stop at 3 layers of depth

Refactor source file collection to use Glob for multiple directories and only go up to 3 layers of depth

Author: Chkoupinator

SConstruct

@@ -38,10 +38,11 @@ Run the following command to download godot-cpp:
 env = SConscript("godot-cpp/SConstruct", {"env": env, "customs": customs})
 
 env.Append(CPPPATH=["src/"])
-for root, folders, files in os.walk("src"):
-    if root.endswith("gen"):
-        continue
-    sources += Glob(os.path.join(root, "*.cpp"))
+
+sources = Glob("src/*.cpp")
+sources.extend(Glob("src/*/*.cpp"))
+sources.extend(Glob("src/*/*/*.cpp"))
+sources.extend(Glob("src/*/*/*/*.cpp"))
 
 if env["target"] in ["editor", "template_debug"]:
     try: