[Bug other/115970] RFE: add support for sending SARIF output to a pipe

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115970

--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
One difference here is that VS code is sending the diagnostics one at a time as
JSON-RPC messages containing SARIF "result" objects as they occur, whereas
currently we write all our SARIF output at once on exit as a single "sarifLog"
object.