Remove unnecessary stack access setup (#7644)

We had a place in emscripten.py where we manually set up stackAlloc etc. This nonstandard location confused metadce, which saw that those functions had extra definitions and uses and hence did not eliminate them.

Removing that extra location reveals the possible reason for it, that it handled the _ prefix difference. Adding those special functions to the list of other special functions (that don't need prefixing) appears makes things work again.

Author: kripken

emscripten.py

@@ -2140,13 +2140,6 @@ def create_module_wasm(sending, receiving, invoke_funcs, jscall_sigs,
 %s;
 ''' % (access_quote('asmGlobalArg'), access_quote('asmLibraryArg'), receiving)]
 
-  module.append('''
-var stackAlloc = Module['_stackAlloc'];
-var stackSave = Module['_stackSave'];
-var stackRestore = Module['_stackRestore'];
-var establishStackSpace = Module['establishStackSpace'];
-''')
-
   module.append(invoke_wrappers)
   module.append(jscall_funcs)
   return module
@@ -2222,7 +2215,7 @@ def asmjs_mangle(name):
   Prepends '_' and replaces non-alphanumerics with '_'.
   Used by wasm backend for JS library consistency with asm.js.
   """
-  library_functions_in_module = ('setThrew', 'setTempRet0', 'getTempRet0')
+  library_functions_in_module = ('setThrew', 'setTempRet0', 'getTempRet0', 'stackAlloc', 'stackSave', 'stackRestore', 'establishStackSpace')
   if name.startswith('dynCall_'):
     return name
   if name in library_functions_in_module: