Ensure a new compiler state object is created every time.

Fixes #225.

static/editor.js

@@ -161,14 +161,19 @@ define(function (require) {
         this.eventHub.on('compileResult', this.onCompileResponse, this);
         this.eventHub.on('selectLine', this.onSelectLine, this);
 
-        var compilerConfig = Components.getCompiler(this.id);
+        // NB a new compilerConfig needs to be created every time; else the state is shared
+        // between all compilers created this way. That leads to some nasty-to-find state
+        // bugs e.g. https://github.com/mattgodbolt/compiler-explorer/issues/225
+        var compilerConfig = _.bind(function () {
+            return Components.getCompiler(this.id);
+        }, this);
 
         this.container.layoutManager.createDragSource(
-            this.domRoot.find('.btn.add-compiler'), compilerConfig);
+            this.domRoot.find('.btn.add-compiler'), compilerConfig());
         this.domRoot.find('.btn.add-compiler').click(_.bind(function () {
             var insertPoint = hub.findParentRowOrColumn(this.container) ||
                 this.container.layoutManager.root.contentItems[0];
-            insertPoint.addChild(compilerConfig);
+            insertPoint.addChild(compilerConfig());
         }, this));
 
         Sharing.initShareButton(this.domRoot.find('.share'), container.layoutManager);
@@ -267,7 +272,7 @@ define(function (require) {
         this.maybeEmitChange(true);
     };
 
-    Editor.prototype.onCompiling = function(compilerId) {
+    Editor.prototype.onCompiling = function (compilerId) {
         this.busyCompilers[compilerId] = true;
     };