* Caching cases compiler invocations to be omitted. You can try this for
yourself by turning on caching while building the project from the
`xcode-hello` integration test, then cleaning of the build artifacts
and building the project again while caching is enabled. This yields
a database that is practically empty.
* The integrated driver causes compiler invocations to depend on modules
shipped with Xcode. Those are unfortunately incompatible with our
extractor.
Previously, we were using 8.0.0rc1.
In particular, this upgrade means we need to explicitly
import more rules, as they've been moved out of the core bazel repo.
`pod install` could generate Xcode projects files needed for
autobuilding, so it's better to install dependencies first, and then do
re-scan to pick up the new files.
