Hello! GitHub Actions runners recently upgraded to CMake 3.20 on Windows, which broke our build. After some investigation, we found out that a variable we have set as an `option` called `TOOL` is set before our call to `option`, leaving it to its default value (which seems empty?). For some reason, if we run CMake twice (with a cache), the `TOOL` option is set correctly. For now, I guess our workaround is to prefix all these variables with something unique like our project name, but this extends our command line length by quite a lot. I can reproduce this with the following CMakeLists.txt on Windows with the VS2019 generator and MSVC: ``` cmake_minimum_required(VERSION 3.20.0) project(foobar) option(TOOL "This variable doesn't work" TRUE) option(NOT_TOOL "This variable does work" TRUE) file(GENERATE OUTPUT foo.cpp CONTENT "int main(){return 0;}") if (TOOL) add_library(lib foo.cpp) endif() if (NOT_TOOL) add_library(not_lib foo.cpp) endif() add_executable(bin foo.cpp) add_dependencies(bin lib not_lib) ``` This should fail to generate because `lib` is not defined. Adding `unset(TOOL)` in front of the `option` call should let it build, though this defeats the purpose of the option! Please let me know if I can provide more information regarding this issue!