[PDB] Correctly use the target machine when writing DBI stream.

Using Config->is64() will treat ARM64 as Amd64, which is incorrect.
Furthermore, there are more esoteric architectures that could
theoretically be encountered.  Just set it directly to the machine
type, which we already know anyway.

llvm-svn: 330157
diff --git a/lld/COFF/PDB.cpp b/lld/COFF/PDB.cpp
index 9aa4c64..c2b0826 100644
--- a/lld/COFF/PDB.cpp
+++ b/lld/COFF/PDB.cpp
@@ -1102,8 +1102,7 @@
   pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
   DbiBuilder.setAge(BuildId.PDB70.Age);
   DbiBuilder.setVersionHeader(pdb::PdbDbiV70);
-  DbiBuilder.setMachineType(Config->is64() ? pdb::PDB_Machine::Amd64
-                                           : pdb::PDB_Machine::x86);
+  DbiBuilder.setMachineType(Config->Machine);
   // Technically we are not link.exe 14.11, but there are known cases where
   // debugging tools on Windows expect Microsoft-specific version numbers or
   // they fail to work at all.  Since we know we produce PDBs that are