[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/lib/MC/MCAsmInfoWasm.cpp b/llvm/lib/MC/MCAsmInfoWasm.cpp
index 65a937b..ce6ec7e 100644
--- a/llvm/lib/MC/MCAsmInfoWasm.cpp
+++ b/llvm/lib/MC/MCAsmInfoWasm.cpp
@@ -18,6 +18,7 @@
 
 MCAsmInfoWasm::MCAsmInfoWasm() {
   HasIdentDirective = true;
+  HasNoDeadStrip = true;
   WeakRefDirective = "\t.weak\t";
   PrivateGlobalPrefix = ".L";
   PrivateLabelPrefix = ".L";