kconfig_compiler/CMakeLists.txt - use CMAKE_CROSSCOMPILING
use the CMake variable CMAKE_CROSSCOMPILING to detect when cross-compiling instead of CMAKE_TOOLCHAIN_FILE.
CMAKE_TOOLCHAIN_FILE can be set when not cross-compiling
use the CMake variable CMAKE_CROSSCOMPILING to detect when cross-compiling instead of CMAKE_TOOLCHAIN_FILE.
CMAKE_TOOLCHAIN_FILE can be set when not cross-compiling