[llvm] [Support] Better error msg when cache dir can't be created. (PR #69575)

[David Blaikie via llvm-commits]

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@@ -145,7 +145,8 @@ Expected<FileCache> llvm::localCache(const Twine &CacheNameRef,
       // ensures the filesystem isn't mutated until the cache is.
       if (std::error_code EC = sys::fs::create_directories(
               CacheDirectoryPath, /*IgnoreExisting=*/true))
-        return errorCodeToError(EC);
+        return createStringError(EC, Twine("Can't create cache directory: ") +
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dwblaikie wrote:

(& any test coverage for this?)

https://github.com/llvm/llvm-project/pull/69575