Do not rewrite cmake-tools-kits.json each time on start, throwing away user changes

Each time I start VS Code, the extension seems to rescan Qt versions and rewrite cmake-tools-kits.json in my user settings. It also discards any changes I make to the detected Qt kits.

My use case is this: I'm cross-compiling an app from Windows to Linux ARM board, so I built Qt from source. I registered my Qt installation, providing a path to qmake executable. But I'm unable to specify cross-compilers paths for that kit (my local compiler is invoked instead), nor am I able to add an extra CMake variable.

I worked around this issue by using the cross-compiler kit detected by CMake Tools extension itself, and adding extra CMake variable in settings.json file in my workspace.