Remove testing flag --internal_do_not_export_builtins

Also add a @VisibleForTesting accessor to SkyframeExecutor.

RELNOTES: None
PiperOrigin-RevId: 179875655
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSemantics.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSemantics.java
index 9a6f915..c816cd6 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSemantics.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSemantics.java
@@ -58,7 +58,6 @@
   public abstract boolean incompatibleNewActionsApi();
   public abstract boolean incompatibleShowAllPrintMessages();
   public abstract boolean incompatibleStringIsNotIterable();
-  public abstract boolean internalDoNotExportBuiltins();
   public abstract boolean internalSkylarkFlagTestCanary();
 
   /** Returns a {@link Builder} initialized with the values of this instance. */
@@ -90,10 +89,9 @@
           .incompatibleLoadArgumentIsLabel(true)
           .incompatibleNewActionsApi(false)
           .incompatibleShowAllPrintMessages(true)
-          .incompatibleStringIsNotIterable(false)
-          .internalDoNotExportBuiltins(false)
-          .internalSkylarkFlagTestCanary(false)
-          .build();
+      .incompatibleStringIsNotIterable(false)
+      .internalSkylarkFlagTestCanary(false)
+      .build();
 
   /** Builder for {@link SkylarkSemantics}. All fields are mandatory. */
   @AutoValue.Builder
@@ -119,7 +117,6 @@
     public abstract Builder incompatibleNewActionsApi(boolean value);
     public abstract Builder incompatibleShowAllPrintMessages(boolean value);
     public abstract Builder incompatibleStringIsNotIterable(boolean value);
-    public abstract Builder internalDoNotExportBuiltins(boolean value);
     public abstract Builder internalSkylarkFlagTestCanary(boolean value);
 
     public abstract SkylarkSemantics build();