Fix relative paths

[mateusz-olczyk]

• We're using cwd=tmpdir.name in try_configure() for higher compatibility because -B <path-to-build> was added in CMake version 3.13. This however leads to unexpected results when we pass relative paths as arguments because such paths become relative to the temporary directory, not cwd of shell.
• tools_directory containing CMake downloaded binaries is by default created relatively to current working directory instead of being placed in the root directory of the repository which would make more sense.

Thanks to the proposed changes the following call becomes possible:

❯ cd ~/projects
❯ ~/cmake_min_version/cmake_min_version.py example