When symbols are moved to this module, this module declares them as HIDE
for the OS versions prior to when the move happened. On the other hand, the
original module should declare ADD them for these OS versions. An executable
can choose the right library to link against depending on the deployment target.
This is a walk-around that linker directives cannot specify other install
name per symbol, we should eventually remove this.
Frontend outputs source-as-compiled, and source-ranges file with function body ranges and ranges that were unparsed in secondaries.
Driver computes diffs for each source file. If diffs are in function bodies, only recompiles that one file. Else if diffs are in what another file did not parse, then the other file need not be rebuilt.
We already have something called "module interfaces" -- it's the
generated interface view that you can see in Xcode, the interface
that's meant for developers using a library. Of course, that's also a
textual format. To reduce confusion, rename the new module stability
feature to "parseable [module] interfaces".
...but don't hook it up to anything yet.
This is the very very start of the module stability / textual
interfaces feature described at
https://forums.swift.org/t/plan-for-module-stability/14551/
For now I've just made it a frontend option (not a driver option),
which is good enough for testing.
This means moving the output path into SupplementaryOutputPaths, and
using the same sort of diagnostic dispatching that serialized
diagnostics use. This is part of what's needed to run the migrator
in batch mode.
