Expose late-bound-attributes to Skylark.

RELNOTES: Late-bound attributes are exposed to skylark. This is a new API (`configuration_field()`) to depend on certain configuration-defined targets from skylark rules.
PiperOrigin-RevId: 174534104
diff --git a/src/main/java/com/google/devtools/build/lib/packages/RuleClassProvider.java b/src/main/java/com/google/devtools/build/lib/packages/RuleClassProvider.java
index 5235523..302b05b 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/RuleClassProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/RuleClassProvider.java
@@ -93,4 +93,10 @@
    * Retrieves an aspect from the aspect factory map using the key provided
    */
   NativeAspectClass getNativeAspectClass(String key);
+
+  /**
+   * Retrieves a {@link Map} from skylark configuration fragment name to configuration fragment
+   * class.
+   */
+  Map<String, Class<?>> getConfigurationFragmentMap();
 }