When opening broken symlink with O_CREAT, replace it

For the purposes of open, linux seems to treat a broken link as not existing.

Author: hoodmane

src/library_fs.js

@@ -1021,17 +1021,24 @@ FS.staticInit();
         mode = 0;
       }
       var node;
+      var isBrokenLink;
       if (typeof path == 'object') {
         node = path;
       } else {
         path = PATH.normalize(path);
         try {
-          var lookup = FS.lookupPath(path, {
-            follow: !(flags & {{{ cDefs.O_NOFOLLOW }}})
-          });
+          var lookup = FS.lookupPath(path);
           node = lookup.node;
+          if ((!(flags & {{{ cDefs.O_NOFOLLOW }}})) && node && FS.isLink(node.mode)) {
+            var lookup = FS.lookupPath(path, {follow: true});
+            node = lookup.node;
+          }
         } catch (e) {
-          // ignore
+          // If node is defined but we raised an error, it's because the first
+          // lookup succeeded but the lookup with follow raised ENOENT. Thus, we
+          // have a broken symlink.
+          isBrokenLink = !!node;
+          node = undefined;
         }
       }
       // perhaps we need to create the node
@@ -1044,6 +1051,10 @@ FS.staticInit();
           }
         } else {
           // node doesn't exist, try to create it
+          if (isBrokenLink) {
+            // If there's a broken link we have to remove it first
+            FS.unlink(path);
+          }
           node = FS.mknod(path, mode, 0);
           created = true;
         }