rts: include the filter file in script_test when the rts arg is set

A new model of test selection is being developed. This requires us to
bring back all the infrastructure around test selection.
https://crrev.com/c/5954865 brought back the dummy file creation but
left this file out of the deps causing it to not be included in the
isolate and the harness to complain it's not there

Bug: 375000947
Change-Id: I64d1856600722625875438fd45ced1d2c2bb7762
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6089056
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Commit-Queue: Struan Shrimpton <sshrimp@google.com>
Cr-Commit-Position: refs/heads/main@{#1395072}