Turbopack + Relay: correctly implement artifact_directory to fix multi-project test (#8655)
Previously, if `artifact_directory` were set, artifacts would be
resolved at a fixed location relative to each file. This correctly
resolves them from the project root.
Test Plan: With vercel/next.js#67403, `TURBOPACK_BUILD=1 TURBOPACK=1
pnpm test-dev
test/integration/relay-graphql-swc-multi-project/test/index.test.js`