[WebAssembly] Add a EM_WEBASSEMBLY value, and several bits of code that use it.

A request has been made to the official registry, but an official value is
not yet available. This patch uses a temporary value in order to support
development. When an official value is recieved, the value of EM_WEBASSEMBLY
will be updated.

llvm-svn: 257517
diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cpp
index 62c27cc..12b772d 100644
--- a/llvm/lib/Object/ELF.cpp
+++ b/llvm/lib/Object/ELF.cpp
@@ -91,6 +91,13 @@
       break;
     }
     break;
+  case ELF::EM_WEBASSEMBLY:
+    switch (Type) {
+#include "llvm/Support/ELFRelocs/WebAssembly.def"
+    default:
+      break;
+    }
+    break;
   default:
     break;
   }