LABEL attribute with split transitions should always be lists of Targets
in Skylark rule context.

--
MOS_MIGRATED_REVID=126405174

src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java

diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
index a956e4d..8112e02 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
@@ -311,7 +311,7 @@
       filesBuilder.put(
           skyname, ruleContext.getPrerequisiteArtifacts(a.getName(), Mode.DONT_CHECK).list());
       List<?> allPrereq = ruleContext.getPrerequisites(a.getName(), Mode.DONT_CHECK);
-      if (type == BuildType.LABEL) {
+      if (type == BuildType.LABEL && !a.hasSplitConfigurationTransition()) {
         Object prereq = ruleContext.getPrerequisite(a.getName(), Mode.DONT_CHECK);
         if (prereq == null) {
           prereq = Runtime.NONE;