Silence echo in do command within run_python_compiler.bat

The emscan-deps.bat file produces invalid dynamic dependency files, suffix `.ddi`, due to the `do` command being echoed. The output of the scan step is used to create a temporary file that then is renamed into the built .ddi file. 

Example of emscripten build generated file:
```

D:\emscriptenDebug\out>() 
{
  "revision": 0,
  "rules": [
    {
      "primary-output": "CMakeFiles\\demoApp.dir\\demoApp.cpp.o"
    }
  ],
  "version": 1
}
```

This file should be a validly formed JSON document, instead we have a blank line and a line produced by the `do` command preceding the JSON document

This commit represents one proposed solution

Author: MarcosASandoval

tools/maint/run_python_compiler.bat

@@ -2,8 +2,8 @@
 ::
 :: Automatically generated by `create_entry_points.py`; DO NOT EDIT.
 ::
-:: To make modifications to this file, edit `tools/run_python_compiler.bat` and
-:: then run `tools/create_entry_points.py`
+:: To make modifications to this file, edit `tools/maint/run_python_compiler.bat` and
+:: then run `tools/maint/create_entry_points.py`
 
 :: N.b. In Windows .bat scripts, the ':' character cannot appear inside any if () blocks,
 :: or there will be a parsing error.
@@ -26,7 +26,7 @@
   set "MYDIR=%~dp0"
   goto FOUND_MYDIR
 )
-@for %%I in (%~n0.bat) do (
+@for %%I in (%~n0.bat) do @(
   @if exist %%~$PATH:I (
     set MYDIR=%%~dp$PATH:I
   ) else (