clang-scan-deps fails to parse C++ files when comparing a macro against a numeric literal that contains digit separators in preprocessor.

clang version 21.1.8
Target: x86_64-w64-windows-gnu
Thread model: posix

```cpp
#if __cplusplus >= 2020'00L
#endif

int main(int argc, char *argv[])
{
return 0;
}
```
clang-scan-deps fails with such error
`test.cpp:1:24: error: token is not a valid binary operator in a preprocessor subexpression`

Accroding to CMake policy [CMP0155](https://cmake.org/cmake/help/latest/policy/CMP0155.html)
> CMake 3.27 and below assume that C++ sources do not import modules. CMake 3.28 and above prefer to assume that C++ sources in targets using C++20 or higher might import modules, and must be scanned before compiling, unless explicitly disabled.

clang-scan-deps is always invoked with CMake 3.28+ and C++20 or higher, even if I am not utilizing C++ module features. (I encounter the bug in NIVADIA/stdexec library where there are many feature testing macros used with numeric literals which contain digit separators.)

Reproduce the failure with the test.cpp example using clang-scan-deps, then trace how its preprocessor evaluates the #if comparison containing a digit separator. Compare this path with ordinary C++ preprocessing, and add coverage so the sample parses successfully without the reported error.

Written by the indexing model from the issue text.