JS: fs module imported twice (by emscripten and by ghc-internal). ghc-internal import wrapped

in a closure to prevent conflict with emscripten (fixes #24602)

Better solution is to use some JavaScript module system like AMD, CommonJS or even UMD. It will be investigated at other issues.
At first glance we should try UMD (See https://github.com/umdjs/umd)

libraries/ghc-internal/jsbits/platform.js

@@ -46,18 +46,36 @@ function h$isGHCJSi() {
 }
 
 // load all required node.js modules
-if(typeof process !== 'undefined' && (typeof h$TH !== 'undefined' || (typeof require !== 'undefined' && typeof module !== 'undefined' && module.exports))) {
+if(typeof global !== 'undefined' && typeof process !== 'undefined' && (typeof h$TH !== 'undefined' || (typeof require !== 'undefined' && typeof module !== 'undefined' && module.exports))) {
     h$isNode_ = true;
-    // we have to use these names for the closure compiler externs to work
-    var fs            = require('fs');
-    var path          = require('path');
-    var os            = require('os');
-    var child_process = require('child_process');
-    var h$fs          = fs;
-    var h$path        = path;
-    var h$os          = os;
-    var h$child       = child_process;
+    // we have to put fs var into closure to prevent name clashes with emscripten compiler code injections
+    // we use additional suffix to have more guarantees over possible clashes
+    // we should use amd/commonjs module wrappers to avoid such ugly things
+    global.h$nodeOS_modules_qvsKGchAmE = (function() {
+      var fs = require('fs');
+      var path = require('path');
+      var os = require('os');
+      var child_process = require('child_process');
+      return {
+        'fs' : fs,
+        'path': path,
+        'os': os,
+        'child_process': child_process
+      };
+    })();
+    // we dictionary-like access strictly prevents
+    // google closure compiler names mangling
+    var h$fs          = global.h$nodeOS_modules_qvsKGchAmE['fs'];
+    var h$path        = global.h$nodeOS_modules_qvsKGchAmE['path'];
+    var h$os          = global.h$nodeOS_modules_qvsKGchAmE['os'];
+    var h$child       = global.h$nodeOS_modules_qvsKGchAmE['child_process'];
+
+    // we forcibly delete temporary lexical environment variable
+    // to prevent any clashes
+    delete global.h$nodeOS_modules_qvsKGchAmE;
+
     var h$process     = process;
+
     function h$getProcessConstants() {
       // this is a non-public API, but we need these values for things like file access modes
       var cs = process['binding']('constants');