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

[Samarth Narang via cfe-commits]

snarang181 wrote:

Also, from the CI test run, I see the Linux build failing. This seems unrelated, right? Does it warrant a rerun? 
```
/home/gha/actions-runner/_work/llvm-project/llvm-project/libc/test/src/math/smoke/HypotTest.h:31: FAILURE
Failed to match aNaN against LIBC_NAMESPACE::testing::getMatcher< LIBC_NAMESPACE::testing::TestCond::EQ>(func(sNaN, neg_inf)).
Expected floating point value: (+Infinity)
Actual floating point value: (NaN)
[  FAILED  ] LlvmLibcHypotf16Test.SpecialNumbers
Ran 1 tests.  PASS: 0  FAIL: 1/home/gha/actions-runner/_work/llvm-project/llvm-project/libc/test/src/math/smoke/HypotTest.h:31: FAILURE
Failed to match aNaN against LIBC_NAMESPACE::testing::getMatcher< LIBC_NAMESPACE::testing::TestCond::EQ>(func(sNaN, neg_inf)).
Expected floating point value: (+Infinity)
Actual floating point value: (NaN)
[  FAILED  ] LlvmLibcHypotf16Test.SpecialNumbers
Ran 1 tests.  PASS: 0  FAIL: 1
```

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