Add libinteraction to .gn check_targets list

libinteraction is used in certain internal builds.

Bug: b/110808839
Change-Id: I51c29bd0033d608413e97029f288de44b89fc441
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1560138
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Luke Halliwell <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649229}