Added missing cmakeToolchain path setting to windows_buildenv.bat

[JoergAtGithub]

Without this setting the CMake cache is uneccessary often invalidated, which requires complete recompile. With this setting switching between different branches and build configurations doesn't require a full rebuild in most cases.

[ronso0]

just a side note: you can keep the commit message subject short (use PR title, ~50 chars max recommended) and put the detailed description into the message body (wrapping at 70-75, recommendations vary ; )

[daschuer]

now cmakeToolchain is passed as -DCMAKE_TOOLCHAIN_FILE to cmake.
Howerver it was already set here:

mixxx/CMakeLists.txt

Line 63 in 74ec345

set(CMAKE_TOOLCHAIN_FILE "${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake" CACHE STRING "")

if VCPKG_ROOT is set which should be the case.

Please explain how this PR makes a difference and how it prevents rebuilding.

[JoergAtGithub]

Indeed, this looks like the same to me. Somehow my addition helped - currently I can't explain this.

[daschuer]

Can you double check it, before merge?

[JoergAtGithub]

I checked this again, while testing the different built targets with the new builenv. It doesn't work without this setting in CMakeSettings.json. The CMake cache is always invalidated, when I change the target.
I can't explain, why the setting in CMakelists.txt doesn't work here too, but the result is reproduceable.

[daschuer]

OK, It is still weird. But passing the CMAKE_TOOLCHAIN_FILE via CMakeSetting.json is the standard, so let's go for it.

[JoergAtGithub]

Thanks!