[BOLT] Support perf2bolt-N in the driver

Check invoked tool with `starts_with`.

Addresses the issue where `perf2bolt` invoked using a distro symlink
`perf2bolt-16` fails to run in perf2bolt mode and runs in llvm-bolt mode
instead.

The issue is mentioned in https://vondra.me/posts/playing-with-bolt-and-postgres/

Test Plan:
```
ln -sf perf2bolt perf2bolt-20
perf2bolt-20 clang -p perf.data -o fdata.clang -w yaml.clang
...
PERF2BOLT: wrote 188593 objects and 0 memory objects to fdata.clang
```

Reviewers: ayermolo, rafaelauler, dcci, maksfb

Reviewed By: maksfb

Pull Request: llvm#111072

Author: aaupov

bolt/tools/driver/llvm-bolt.cpp

@@ -202,9 +202,9 @@ int main(int argc, char **argv) {
 
   ToolName = argv[0];
 
-  if (llvm::sys::path::filename(ToolName) == "perf2bolt")
+  if (llvm::sys::path::filename(ToolName).starts_with("perf2bolt"))
     perf2boltMode(argc, argv);
-  else if (llvm::sys::path::filename(ToolName) == "llvm-boltdiff")
+  else if (llvm::sys::path::filename(ToolName).starts_with("llvm-boltdiff"))
     boltDiffMode(argc, argv);
   else
     boltMode(argc, argv);