When running west zephyr-export on Windows, the command fails if nmake is not in the PATH, even if ninja is installed and available

[MOYUtianming]

Describe the bug

This is because the underlying cmake command is invoked without a -G generator argument, causing CMake to default to "NMake Makefiles" on Windows.

Regression

• This is a regression.

Steps to reproduce

1. On a Windows machine with ninja installed but without Visual Studio build tools (nmake) in the PATH.
2. follow the steps for install zephyr on windows in https://docs.zephyrproject.org/latest/develop/getting_started/index.html until Run west zephyr-export.

Relevant log output

FATAL ERROR: command exited with status 1: '.../cmake.EXE' -S '...' -B '...'
CMake Error at CMakeLists.txt:12 (project):
  Running
   'nmake' '-?'
  failed with:
   no such file or directory

Impact

Annoyance – Minor irritation; no significant impact on usability or functionality.

Environment

OS: Windows
Toolchain: Zephyr SDK, CMake, Ninja

Additional Context

Using a PowerShell command line in a format similar to the one below:
& 'C:\Program Files\CMake\bin\cmake.EXE' -S '\zephyrproject\zephyr\share\zephyr-packge\cmake' -B '\zephyrproject\zephyr\share\zephyr-packge\cmake' -G Ninja
to replace
west zephyr-export
allows this step to be successfully completed in this installation.

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