Make PackageLookupValue#key(PathFragment) public.

RELNOTES: None
PiperOrigin-RevId: 166907799
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/PackageLookupValue.java b/src/main/java/com/google/devtools/build/lib/skyframe/PackageLookupValue.java
index 4bf711f..875edb0 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/PackageLookupValue.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/PackageLookupValue.java
@@ -150,7 +150,7 @@
    */
   public abstract String getErrorMsg();
 
-  static SkyKey key(PathFragment directory) {
+  public static SkyKey key(PathFragment directory) {
     Preconditions.checkArgument(!directory.isAbsolute(), directory);
     return key(PackageIdentifier.createInMainRepo(directory));
   }