Build 64-bit cameraservice on 64-bit-only

Bug: 135535544
Change-Id: I57f18ba105454dd609d0a3a4684fbfecf103144d
diff --git a/camera/cameraserver/Android.bp b/camera/cameraserver/Android.bp
index 320c499..89c782d 100644
--- a/camera/cameraserver/Android.bp
+++ b/camera/cameraserver/Android.bp
@@ -36,7 +36,7 @@
         "android.hardware.camera.device@3.2",
         "android.hardware.camera.device@3.4",
     ],
-    compile_multilib: "32",
+    compile_multilib: "prefer32",
     cflags: [
         "-Wall",
         "-Wextra",