Don't add API annotations in the internal R.java

I'm trying to enable a check for the following structure:
```
/** @hide */
public class Class1 {
    /** @hide */
    @SystemApi // Invalid because the class is hidden.
    public void method1() { }
}
```

The internal R.java file violates this, which this change is going to fix.

Bug: 159162473
Test: build (treehugger)
Test: atest aapt2_tests

Change-Id: I613e8611ddaf5f8e4761d351d4cd0142d59c7cc9
diff --git a/tools/aapt2/cmd/Link.cpp b/tools/aapt2/cmd/Link.cpp
index 3a3fb28..72cb41a 100644
--- a/tools/aapt2/cmd/Link.cpp
+++ b/tools/aapt2/cmd/Link.cpp
@@ -1272,7 +1272,8 @@
       return false;
     }
 
-    ClassDefinition::WriteJavaFile(manifest_class.get(), package_utf8, true, &fout);
+    ClassDefinition::WriteJavaFile(manifest_class.get(), package_utf8, true,
+                                   false /* strip_api_annotations */, &fout);
     fout.Flush();
 
     if (fout.HadError()) {