Capture/Replay: Fix GN build when JSON not available. This change makes it so we no longer build frame capture when JSON is not available. In Skia's build this is the case. Also updates the GN scripts to use a new variable 'angle_has_frame_capture'. Bug: angleproject:5133 Bug: angleproject:6374 Change-Id: I30290a160f6ebe6419f371e36d304a61bf0a85ac Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3152557 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>