[WebAssembly] Don't create a needless .note.GNU-stack section

WebAssembly's stack will never be executable by default, so it isn't
necessary to declare .note.GNU-stack sections to request a non-executable
stack.

Differential Revision: http://reviews.llvm.org/D15969

llvm-svn: 257962
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
index 02c717a..84c77d2 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
@@ -48,4 +48,7 @@
   ExceptionsType = ExceptionHandling::None;
 
   // TODO: UseIntegratedAssembler?
+
+  // WebAssembly's stack is never executable.
+  UsesNonexecutableStackSection = false;
 }