[clang] [llvm] [llvm] properly guard dump methods in Support lib classes (PR #139938)

[Harald van Dijk via cfe-commits]

hvdijk wrote:

Minimal reproducer is
```c++
#include <llvm/IR/ModuleSummaryIndex.h>
int main() {}
```
Compile and link this without any special options (specifically: without `-DNDEBUG`) against an LLVM release build, and it will now fail.

https://github.com/llvm/llvm-project/pull/139938