Fix ``The system cannot find the drive specified.`` due to ``::`` style comments used in function block in emsdk.bat (#627)

diff --git a/emsdk.bat b/emsdk.bat
index 4ba706e..66f6d11 100644
--- a/emsdk.bat
+++ b/emsdk.bat
@@ -4,11 +4,11 @@
 

 setlocal

 

+:: When using our bundled python we never want the users

+:: PYTHONHOME or PYTHONPATH

+:: https://github.com/emscripten-core/emsdk/issues/598

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

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

-  :: When using our bundled python we never want the users

-  :: PYTHONHOME or PYTHONPATH

-  :: https://github.com/emscripten-core/emsdk/issues/598

   set PYTHONHOME=

   set PYTHONPATH=

   goto end