COFF: Use short identifiers. NFC.

llvm-svn: 243229
diff --git a/lld/COFF/InputFiles.cpp b/lld/COFF/InputFiles.cpp
index 3e6a6b9..e9008d0 100644
--- a/lld/COFF/InputFiles.cpp
+++ b/lld/COFF/InputFiles.cpp
@@ -367,11 +367,11 @@
     return IMAGE_FILE_MACHINE_UNKNOWN;
   switch (Triple(M->getTargetTriple()).getArch()) {
   case Triple::x86_64:
-    return IMAGE_FILE_MACHINE_AMD64;
+    return AMD64;
   case Triple::x86:
-    return IMAGE_FILE_MACHINE_I386;
+    return I386;
   case Triple::arm:
-    return IMAGE_FILE_MACHINE_ARMNT;
+    return ARMNT;
   default:
     return IMAGE_FILE_MACHINE_UNKNOWN;
   }