Enable API modelling for D8 CLI

It has been enabled for R8 CLI for a long time, and has also been
enabled by default in AGP for more than an year.

Change-Id: Ibc21a5e91d90ce41499499ec41d26ecc369937e7

src/main/java/com/android/tools/r8/D8CommandParser.java

diff --git a/src/main/java/com/android/tools/r8/D8CommandParser.java b/src/main/java/com/android/tools/r8/D8CommandParser.java
index a16189b..a6e5d5f 100644
--- a/src/main/java/com/android/tools/r8/D8CommandParser.java
+++ b/src/main/java/com/android/tools/r8/D8CommandParser.java
@@ -396,6 +396,8 @@
     if (globalsOutputPath != null) {
       builder.setGlobalSyntheticsOutput(globalsOutputPath);
     }
-    return builder.setOutput(outputPath, outputMode);
+    builder.setOutput(outputPath, outputMode);
+    builder.setEnableExperimentalMissingLibraryApiModeling(true);
+    return builder;
   }
 }