Correctly write links to paths remapped using --path-equivalence

The coverage scripts rewrite the displayed paths in the reports so
that they reflect the source layout of the repo since that is more
intuitive for developers. The actual report files are in report
directory in the lcov layout created by lcov, so the links in the
report need to use the unmapped values to point to the correct file
location.

Bug: 498083630
Change-Id: Ibdc2cf3f43689b44e8bfde96d63f25b9dd82f06e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7780761
Reviewed-by: Jeff Yoon <jeffyoon@google.com>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Auto-Submit: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1618843}
NOKEYCHECK=True
GitOrigin-RevId: 92d41fddbd04df9b465f71718b8a711ab1d00776