[Release][C++] Windows source verification should not mutate source tree

`verify-release-candidate.bat` creates a temporary dir for verification, but for some reason it still creates its CMake build dir inside the Arrow source tree. It should instead create the CMake build dir inside the temporary verification dir.

**Reporter**: [Antoine Pitrou](https://issues.apache.org/jira/browse/ARROW-16322) / @pitrou

_{**Note**: *This issue was originally created as [ARROW-16322](https://issues.apache.org/jira/browse/ARROW-16322). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start with verify-release-candidate.bat and trace where it creates the temporary verification directory and invokes CMake. Run the Windows source verification and check that the CMake build directory is inside the temporary verification directory, with no build directory or other mutations left in the Arrow source tree.

Written by the indexing model from the issue text.