[CMake] Update lit test configuration

There are several changes:
- Don't stringify Pythonized bools (that's why we're Pythonizing them)
- Support specifying target and sysroot via CMake variables
- Use consistent spelling for --target, --sysroot, --gcc-toolchain

llvm-svn: 353137
GitOrigin-RevId: 3ad50fed488b52e93aee5ce5607055aa77207c14
2 files changed