ci(release): fix MSI release build rootfs path

[pendo324]

Issue #, if available:

• MSI release builds are broken, as seen in this automated run
  • Debugged by looking at the lima stderr logs and found:

  {"level":"fatal","msg":"failed to download \"file://C:/actions-runner/_work/finch/finch/_output/os/finch-rootfs-production-amd64-1719439880.tar.gz\": open C:/actions-runner/_work/finch/finch/_output/os/finch-rootfs-production-amd64-1719439880.tar.gz: The system cannot find the path specified.","time":"2024-07-02T19:14:36Z"}
  

Description of changes:

• This regression occurred because FINCH_ROOTFS_LOCATION_ROOT was removed from the Makefile during recent refactoring. FINCH_ROOTFS_LOCATION_ROOT was used to override the path of the rootfs file used at runtime by Lima. Removing it means that release builds, which are installed to different locations than dev builds, will not function. This PR makes it so Windows follows the macOS Makefile variable name (FINCH_OS_IMAGE_LOCATION_ROOT), as seen in ci(release): fix release build generation #1007

Testing done:

• I've reviewed the guidance in CONTRIBUTING.md

License Acceptance

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[pendo324]

Confirmed Finch VM was able to start in the release workflow: https://github.com/runfinch/finch/actions/runs/9767086718/job/26961647512#step:13:56

Confirmed we can manually kick off release builds from different source tags using the ref_name input: https://github.com/runfinch/finch/actions/runs/9767146410/job/26961744190#step:9:19

(I cancelled both workflows so that we can use the resources to run from main instead of this branch)

PTAL again @austinvazquez