[WebAssembly] Add -m:e to the target triple.

This enables ELF-style name mangling, which primarily means using ".L" for
private symbols.

llvm-svn: 257020
diff --git a/llvm/test/CodeGen/WebAssembly/vtable.ll b/llvm/test/CodeGen/WebAssembly/vtable.ll
index 38298bc..739ba2a 100644
--- a/llvm/test/CodeGen/WebAssembly/vtable.ll
+++ b/llvm/test/CodeGen/WebAssembly/vtable.ll
@@ -11,7 +11,7 @@
 ;   struct D : public B;
 ; Each with a virtual dtor and method foo.
 
-target datalayout = "e-p:32:32-i64:64-n32:64-S128"
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown"
 
 %struct.A = type { i32 (...)** }