setting paths in cmakepresets.json to be in CMAKE format

In cmakepresets.json file, you can set a cacheVariable like the following:

  "CMAKE_PREFIX_PATH": "$env{PATH};${sourceDir}/dependencies"

The problem is that in windows, $env{PATH} will have backslashes "\" to define directories, where ${sourceDir} will use the CMAKE convention of forward slashes "/" meaning that the CMAKE_PREFIX_PATH will be incorrectly set with a mixture of both.

it is suggested that either cmake "generator expressions" are supported in cmakepresets.json, or a special macro is provided to enable getting the paths to all work together correctly