Simplify makeModuleReceiveWithVar. NFC (#22356)

This means that makeModuleReceiveWithVar results in a single statements
instead of two:

var foo = Module['foo'];

vs:

var foo; if (Module['foo']) foo = Module['foo'];

Saves a little on code size.

Author: sbc100

src/parseTools.mjs

@@ -866,8 +866,7 @@ function makeModuleReceiveWithVar(localName, moduleName, defaultValue, noAssert)
     if (defaultValue) {
       ret += ` = Module['${moduleName}'] || ${defaultValue};`;
     } else {
-      ret += `; ${makeModuleReceive(localName, moduleName)}`;
-      return ret;
+      ret += ` = Module['${moduleName}'];`;
     }
   }
   if (!noAssert) {

src/preamble.js

@@ -34,6 +34,14 @@ if (Module['doWasm2JS']) {
 #endif
 #endif
 
+#if MAYBE_WASM2JS
+if (WebAssembly.isWasm2js) {
+  // We don't need to actually download a wasm binary, mark it as present but
+  // empty.
+  wasmBinary = [];
+}
+#endif
+
 #if ASSERTIONS && WASM == 1
 if (typeof WebAssembly != 'object') {
   err('no native wasm support detected');

src/wasm2js.js

@@ -87,10 +87,9 @@ WebAssembly = {
     };
   },
 
-  RuntimeError: Error
-};
+  RuntimeError: Error,
 
 #if !MINIMAL_RUNTIME
-// We don't need to actually download a wasm binary, mark it as present but empty.
-wasmBinary = [];
+  isWasm2js: true,
 #endif
+};

test/other/metadce/test_metadce_cxx_ctors1.gzsize

@@ -1 +1 @@
-8546
+8540

test/other/metadce/test_metadce_cxx_ctors1.jssize

@@ -1 +1 @@
-20923
+20901

test/other/metadce/test_metadce_cxx_ctors2.gzsize

@@ -1 +1 @@
-8530
+8524

test/other/metadce/test_metadce_cxx_ctors2.jssize

@@ -1 +1 @@
-20891
+20869

test/other/metadce/test_metadce_cxx_except.gzsize

@@ -1 +1 @@
-9588
+9581

test/other/metadce/test_metadce_cxx_except.jssize

@@ -1 +1 @@
-24829
+24807

test/other/metadce/test_metadce_cxx_except_wasm.gzsize

@@ -1 +1 @@
-8498
+8492