Add the --experimental_disable_external package command line option that (unsurprisingly) disables the //external package

This has the side effect of allowing labels in the unnamed package to start
with "external" (e.g. //:external/foo/bar)

RELNOTES: None.
PiperOrigin-RevId: 296237592
diff --git a/src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java b/src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java
index b13f2dc..743d169 100644
--- a/src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java
+++ b/src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java
@@ -121,6 +121,7 @@
         // <== Add new options here in alphabetic order ==>
         "--debug_depset_depth=" + rand.nextBoolean(),
         "--experimental_action_args=" + rand.nextBoolean(),
+        "--experimental_disable_external_package=" + rand.nextBoolean(),
         "--experimental_sibling_repository_layout=" + rand.nextBoolean(),
         "--experimental_allow_incremental_repository_updates=" + rand.nextBoolean(),
         "--experimental_aspect_output_propagation=" + rand.nextBoolean(),
@@ -175,6 +176,7 @@
         // <== Add new options here in alphabetic order ==>
         .debugDepsetDepth(rand.nextBoolean())
         .experimentalActionArgs(rand.nextBoolean())
+        .experimentalDisableExternalPackage(rand.nextBoolean())
         .experimentalSiblingRepositoryLayout(rand.nextBoolean())
         .experimentalAllowIncrementalRepositoryUpdates(rand.nextBoolean())
         .experimentalAspectOutputPropagation(rand.nextBoolean())