[vm/sdk] add missing vm entry-point pragma

Rationale:
This makes File/Directory/Link's fromRawPath
equivalent again, and unblocks the pending
loop-based inlining heuristic.

Reverted CL because of this bug:
https://dart-review.googlesource.com/c/sdk/+/81335

#34473
#32167

Change-Id: I769a8365ea32d6f6830d0dd8ef97fc6c2467fb90
Reviewed-on: https://dart-review.googlesource.com/c/81460
Reviewed-by: Vyacheslav Egorov <[email protected]>
Commit-Queue: Aart Bik <[email protected]>

sdk/lib/io/link.dart

@@ -21,6 +21,7 @@ abstract class Link implements FileSystemEntity {
     return overrides.createLink(path);
   }
 
+  @pragma("vm:entry-point")
   factory Link.fromRawPath(Uint8List rawPath) {
     // TODO(bkonyi): handle overrides
     return new _Link.fromRawPath(rawPath);