[WebAssembly] Add symbol flag to the binary format llvm.used

Summary:
Rather than add a new attribute
See https://github.com/WebAssembly/tool-conventions/issues/64

Subscribers: dschuff, jgravelle-google, aheejin, sunfish, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57864

llvm-svn: 353360
diff --git a/llvm/tools/llvm-readobj/WasmDumper.cpp b/llvm/tools/llvm-readobj/WasmDumper.cpp
index 42851ab..9ff222e 100644
--- a/llvm/tools/llvm-readobj/WasmDumper.cpp
+++ b/llvm/tools/llvm-readobj/WasmDumper.cpp
@@ -49,6 +49,7 @@
   ENUM_ENTRY(VISIBILITY_DEFAULT),
   ENUM_ENTRY(VISIBILITY_HIDDEN),
   ENUM_ENTRY(UNDEFINED),
+  ENUM_ENTRY(EXPORTED),
 #undef ENUM_ENTRY
 };