1. `Package.resolved` is copied with the sources, listing 11 remote
pins.
2. `swift-test` hands the resolver both the manifests and those 11 pins.
3. The resolver collects the local path dependencies first. Each
overrides any other reference to the same package.
4. It then prefetches every pin that is not overridden. Four are
overridden and skipped — `swift-driver`, `swift-argument-parser`,
`swift-tools-support-core`, `swift-toolchain-sqlite`. The other seven
are cloned: six have no local dependency under
`SWIFTCI_USE_LOCAL_DEPS=1`, and `swift-llbuild` is local but its
dependency is named for its directory, `llbuild`, while the pin is named
for its repository, `swift-llbuild`, so the override misses.
5. `SWIFTCI_USE_LOCAL_DEPS=1` (which means no networking) is defeated.