[clang] [clang-tools-extra] [clang-tidy] Avoid matching nodes in system headers (PR #151035)

[Carlos Galvez via cfe-commits]

carlosgalvezp wrote:

> Something else to benchmark: https://github.com/llvm/llvm-project/issues/109450.

@firewave Here's the results:

On trunk:

```
6874 warnings generated.
Suppressed 6874 warnings (6874 in non-user code).

real	0m5.298s
user	0m5.209s
sys	0m0.089s
```

With this patch:

```
1949 warnings generated.
Suppressed 1949 warnings (1949 in non-user code).

real	0m1.342s
user	0m1.254s
sys	0m0.089s
```


https://github.com/llvm/llvm-project/pull/151035