[clang][DependencyScanning] Fix StableDir and DependencyActionController Setup for By-Name Lookups

[qiongsiwu]

llvm#164345 merge conflict resolution with next introduced two issues.

1. It did not correctly pick up the logic to set StableDir for CompilerInstanceWithContext.
2. It did not correctly setup the action controller for CAS.

This PR fixes both issues.

[qiongsiwu]

We have tests in swift that catch these two bugs, but I don't think we have any in next. I can look into adding some test cases if that is desired.

[qiongsiwu]

@swift-ci please test llvm

[qiongsiwu]

The two failing tests were failing already before this PR.

Failed Tests (2):
    Clang :: Sema/attr-counted-by-void-ptr-gnu.c
    LLVM :: tools/dsymutil/ARM/cas-gmodule.test

[jansvoboda11]

Yes, please add a test for these. I understand that the missing call to createActionController() didn't cause a test failure - you probably need a new test for this with CAS and by-name scan. But the StableDirs being a local instead of member now surprises me, that should definitely trigger some existing (upstream) test in LLVM, no?

[qiongsiwu]

@swift-ci please test llvm

[qiongsiwu]

I am adding a stable dir test upstream with llvm#168143.

But the StableDirs being a local instead of member now surprises me, that should definitely trigger some existing (upstream) test in LLVM, no?

No because no testing upstream was there tests by-name lookup.

[jansvoboda11]

I am adding a stable dir test upstream with llvm#168143.

But the StableDirs being a local instead of member now surprises me, that should definitely trigger some existing (upstream) test in LLVM, no?

No because no testing upstream was there tests by-name lookup.

I see. Is the upstream test actually broken without this PR? Or what other consequences are there without this PR?

[qiongsiwu]

I am adding a stable dir test upstream with llvm#168143.

But the StableDirs being a local instead of member now surprises me, that should definitely trigger some existing (upstream) test in LLVM, no?

No because no testing upstream was there tests by-name lookup.

I see. Is the upstream test actually broken without this PR? Or what other consequences are there without this PR?

The upstream test passes upstream, but it would be broken if it was in next without this PR. We set StableDirs correctly upstream. See https://github.com/llvm/llvm-project/blob/3f60d220514c4be00e548a17a85c2fa8fa89cc35/clang/lib/Tooling/DependencyScanning/DependencyScannerImpl.cpp#L762. I introduced the bug when I was merging the change into next.