Make readlink system call not resolve the link

Readlink in linux does not resolve the link, it returns the exact link contents.

Author: hoodmane

src/library_fs.js

@@ -895,7 +895,7 @@ FS.staticInit();
       }
 #endif
     },
-    readlink(path) {
+    readlink(path, opts = {}) {
       var lookup = FS.lookupPath(path);
       var link = lookup.node;
       if (!link) {
@@ -904,7 +904,11 @@ FS.staticInit();
       if (!link.node_ops.readlink) {
         throw new FS.ErrnoError({{{ cDefs.EINVAL }}});
       }
-      return PATH_FS.resolve(FS.getPath(link.parent), link.node_ops.readlink(link));
+      const target = link.node_ops.readlink(link);
+      if (opts.noResolve) {
+        return target;
+      }
+      return PATH_FS.resolve(FS.getPath(link.parent), target);
     },
     stat(path, dontFollow) {
       var lookup = FS.lookupPath(path, { follow: !dontFollow });

src/library_syscall.js

@@ -919,7 +919,7 @@ var SyscallsLibrary = {
     path = SYSCALLS.getStr(path);
     path = SYSCALLS.calculateAt(dirfd, path);
     if (bufsize <= 0) return -{{{ cDefs.EINVAL }}};
-    var ret = FS.readlink(path);
+    var ret = FS.readlink(path, {noResolve: true});
 
     var len = Math.min(bufsize, lengthBytesUTF8(ret));
     var endChar = HEAP8[buf+len];