IRGen: adjust the module hash section for COFF

COFF uses 8-character section names.  Adjust the section name for the
module hash from `.swift_modhash` to `.sw5hash` to fit this restriction.

Author: compnerd

lib/IRGen/IRGenModule.cpp

@@ -1047,9 +1047,11 @@ bool IRGenModule::finalize() {
       ModuleHash->setSection("__LLVM,__swift_modhash");
       break;
     case llvm::Triple::ELF:
-    case llvm::Triple::COFF:
       ModuleHash->setSection(".swift_modhash");
       break;
+    case llvm::Triple::COFF:
+      ModuleHash->setSection(".sw5hash");
+      break;
     default:
       llvm_unreachable("Don't know how to emit the module hash for the selected"
                        "object format.");