This cleans up 90 instances of this warning and reduces the build spew
when building on Linux. This helps identify actual issues when
building which can get lost in the stream of warning messages. It also
helps restore the ability to build the compiler with gcc.
Doing so will allow clients to know which Swift-specific PCM arguments are already captured from the scan that first discovered this module.
SwiftDriver, in particular, will be able to use this information to avoid re-scanning a given Clang module if the initial scan was sufficient for all possible sets of PCM arguments on Swift modules that depend on said Clang module.
And only resolve cached dependencies that came from scanning actions with the same target triple.
This change means that the `GlobalModuleDependenciesCache` must be configured with a specific target triple for every scannig action, and it will only resolve previously-found dependencies from previous scannig actions using the exact same triple.
Furthermore, the `GlobalModuleDependenciesCache` separately tracks source-file-based module dependencies as those represent main Swift modules of previous scanning actions, and we must be able to resolve those regardless of the target triple.
Resolves rdar://83105455
Using the serialization format added in https://github.com/apple/swift/pull/37585.
- Add load/save code for the `-scan-dependencies` code-path.
- Add `libSwiftDriver` entry-points to load/store the cache of a given scanner instance.
It is not a distinct result returned by `swiftscan_compiler_supported_arguments_query` and `swiftscan_compiler_supported_features_query`, not owned by any other type, so it must be disposed of by the clients.
For the client library (`libSwiftDriver`), this is critical for multiplexing library instances, and for compatibility with different versions of `libSwiftDrvier`.
Resolves rdar://73631930
This library now relires on a static compiler library called `swiftDependencyScan`, which is also common to being used by `swift-frontend` for its dependency scanner invocations.
