[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/unreachable.ll b/llvm/test/CodeGen/WebAssembly/unreachable.ll
index 414767e..2b03112 100644
--- a/llvm/test/CodeGen/WebAssembly/unreachable.ll
+++ b/llvm/test/CodeGen/WebAssembly/unreachable.ll
@@ -4,7 +4,7 @@
 ; Test that LLVM unreachable instruction and trap intrinsic are lowered to
 ; wasm unreachable
 
-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"
 
 declare void @llvm.trap()