Update emsdk.bat after recent python update

Fixes: #1009
diff --git a/emsdk.bat b/emsdk.bat
index 70e6b70..6842bca 100644
--- a/emsdk.bat
+++ b/emsdk.bat
@@ -14,6 +14,13 @@
   goto end

 )

 

+if exist "%~dp0python\3.9.2-nuget_64bit\python.exe" (

+  set EMSDK_PY="%~dp0python\3.9.2-nuget_64bit\python.exe"

+  set PYTHONHOME=

+  set PYTHONPATH=

+  goto end

+)

+

 if exist "%~dp0python\3.7.4-pywin32_64bit\python.exe" (

   set EMSDK_PY="%~dp0python\3.7.4-pywin32_64bit\python.exe"

   set PYTHONHOME=