Update .gitignore and patch packaging script (#641)

* Update .gitignore

Ignore downloaded NDK
Ignore downloaded EDM4U

* Fix how package tool find EDM4U

When scanning through "*_unity" folders, also check if EDM4U are under
those folders.

Author: chkuang-g

.gitignore

@@ -30,3 +30,10 @@ vcpkg
 
 # Visual Studio Code
 .vscode/
+
+# Downloaded NDK
+ndk/
+ndk_zip
+
+# Downloaded EDM4U
+unity_jar_resolver/

scripts/build_scripts/build_package.py

@@ -116,7 +116,8 @@ def find_pack_script():
   built_folder = None
   resolver_root_folder = "unity-jar-resolver"
   for folder in os.listdir("."):
-    if folder.endswith(built_folder_ext):
+    if (folder.endswith(built_folder_ext) and
+       os.path.exists(os.path.join(folder, built_folder_postion))):
       built_folder = folder
       break