df, Windows: Not compatible with RAM disk

The GitHub action

- name: Setup RAM disk
  if: matrix.job.os == 'windows-latest'
  shell: powershell
  run: |
    choco install imdisk -y
    imdisk -a -s 3G -m Z: -p "/fs:exfat /q /y"
    echo "CARGO_TARGET_DIR=Z:\cargo-target" >> $env:GITHUB_ENV
    echo "TMP=Z:" >> $env:GITHUB_ENV
    echo "TEMP=Z:" >> $env:GITHUB_ENV

caused

failures:
---- filesystem::tests::mount_info_from_path::test_dev_name_match stdout ----
thread 'filesystem::tests::mount_info_from_path::test_dev_name_match' (6148) panicked at src\uu\df\src\filesystem.rs:297:18:
Failed to canonicalize tmp path: Os { code: 1, kind: Uncategorized, message: "Incorrect function." }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
failures:
    filesystem::tests::mount_info_from_path::test_dev_name_match
test result: FAILED. 49 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.02s
error: test failed, to rerun pass `-p uu_df --lib`

Start with src/uu/df/src/filesystem.rs at the canonicalization failure reported near line 297, then run filesystem::tests::mount_info_from_path::test_dev_name_match or cargo test -p uu_df --lib on the Windows RAM-disk setup. Trace why the RAM disk path cannot be canonicalized and verify that the test passes without breaking the other df filesystem tests.