[clang-tools-extra] [clang-doc] Refactor error handling to use ExitOnError (PR #141699)

[Paul Kirth via cfe-commits]

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@@ -0,0 +1,12 @@
+// Test: Invalid output path (%t is a file, not a directory)
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ilovepi wrote:

Since `lit` uses the `IDENTIFIER:` for checks, we shouldn't use `Test:` here to be clear that this is just informational.

There are two common patterns for comments used in LLVM tests: 

1. use an extra comment delimiter eg. `///` in C files or `;;` in LLVM IR. 
2. use the `COM:` directive which is built into FileCheck (https://llvm.org/docs/CommandGuide/FileCheck.html#the-com-directive)

I see (1) far more frequently, but either is fine.

https://github.com/llvm/llvm-project/pull/141699