CMake: specifying build toolchain - makefile

Question

Very new to CMake, and so far I'm finding it to be extremely helpful. I have a set of custom libraries that I would like to build for multiple platforms using cross-compilation. The toolchains are installed, and I can hand-create the Makefiles that I need to do so, but I would like to be able to make use of CMake.
Is there a way to tell cmake which toolchain to use, either at the command line or in the CMakeLists.txt file?

Answer 1

Have a look here: basically, you define a "toolchain file" that sets things like the system name, paths to compilers and so on. You then call cmake like so:
cmake /path/to/src -DCMAKE_TOOLCHAIN_FILE=/path/to/toolchain/foo-bar-baz.cmake

Answer 2

To customize the build settings so you don't have to specify the parameter every time:
For Visual Studio - here
For Vusual Studio Code :
Install the Cmake Tools extension if haven't done so already.
In the .vscode/settings.json file set the parameter cmake.configureArgs. You can also set it from Settings -> CMake Tools configuration -> Add Item. Mine looks like this:
{
"cmake.configureArgs": [
"-DCMAKE_TOOLCHAIN_FILE=C:/Users/.../vcpkg/scripts/buildsystems/vcpkg.cmake"
]
}