Co-authored-by: Christian Clauss <[email protected]>

Fixes nodejs/node-gyp#3296
* nodejs/node-gyp#3296

% `python3.14`
```
>>> import re
>>> s = "TEST_STRING=\\\"TEST\\\""
>>> quote_replacer_regex2 = re.compile(r'(\\+)"')
...
...
... def _EscapeCommandLineArgumentForMSBuild(s):
...     """Escapes a Windows command-line argument for use by MSBuild."""
...
...     def _Replace(match):
...         return (len(match.group(1)) / 2 * 4) * "\\" + '\\"'
...
...     # Escape all quotes so that they are interpreted literally.
...     s = quote_replacer_regex2.sub(_Replace, s)
...     return s
...
>>> _EscapeCommandLineArgumentForMSBuild(s)
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    _EscapeCommandLineArgumentForMSBuild(s)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
  File "<python-input-1>", line 11, in _EscapeCommandLineArgumentForMSBuild
    s = quote_replacer_regex2.sub(_Replace, s)
  File "<python-input-1>", line 8, in _Replace
    return (len(match.group(1)) / 2 * 4) * "\\" + '\\"'
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
TypeError: can't multiply sequence by non-int of type 'float'

>>> Modify _Replace() to use floor division...
>>> _EscapeCommandLineArgumentForMSBuild(s)
'TEST_STRING=\\"TEST\\"'

Fix for Windows test blocking:
* nodejs/node-gyp#/3295

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