Defer creating the CppContext until we have all of its components, so
that we know they're not null. Don't track the action on the context,
since it's not a reliable way of getting back to the compiler invocation
on failure. Don't flush the diagnostics emitter from the emitter
destructor since the derived class emitter will already have been
destroyed at that point. Distinguish between clang setup failing and
clang merely producing errors, and don't connect the check context to
clang if clang setup failed.
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Co-authored-by: David Blaikie <dblaikie@gmail.com>
* Move `Sema` access from `CppFile` into `CppContext`.
* Move the mangle context from `SemIR::File` into `CppContext`.
* Move source location mapping state from `Context` into `CppContext`.
Also factor out the `GenerateAst` function that builds the `CppContext`
and `CppFile` into its own file.
Richard SmithandDavid Blaikie