[LLD] [COFF] Print the file name on errors writing the pdb file

[mstorsjo]

Summary

This avoids confusing contextless error messages such as "No such file or directory" if e.g. the pdb output file should be written to a nonexistent directory. (This can happen with linkrepro scripts, at least old ones.)

As this is more or less NFC, is it ok without a test?

[ruiu]

LGTM

COFF/PDB.cpp

   dbiBuilder.setSectionMap(sectionMap);
 
   // Add COFF section header stream.
   exitOnErr(
       dbiBuilder.addDbgStream(pdb::DbgHeaderType::SectionHdr, sectionTable));
 }
 
 void PDBLinker::commit(codeview::GUID *guid) {
+  ExitOnError exitOnErr((config->pdbPath + ": ").str());
   // Write to a file.
   exitOnErr(builder.commit(config->pdbPath, guid));
 }
 
 static uint32_t getSecrelReloc() {
   switch (config->machine) {
   case AMD64:
     return COFF::IMAGE_REL_AMD64_SECREL;