Disable proguard optimization when not using jack

Proguard optimization causes errors when used with dx:
warning: Ignoring InnerClasses attribute for an anonymous inner class
(android.support.transition.ViewGroupUtilsApi14$1) that doesn't come with an
associated EnclosingMethod attribute. This class was probably produced by a
compiler that did not target the modern .class file format. The recommended
solution is to recompile the class from source, using an up-to-date compiler
and without specifying any "-target" type options. The consequence of ignoring
this warning is that reflective operations on this class will incorrectly
indicate that it is *not* an inner class.
...
Uncaught translation error: com.android.dx.cf.code.SimException: local variable type mismatch: attempt to set or access a value of type android.service.notification.StatusBarNotification[] using a local variable of type java.lang.String. This is symptomatic of .class transformation tools that ignore local variable information.
Uncaught translation error: com.android.dx.cf.code.SimException: local variable type mismatch: attempt to set or access a value of type com.google.common.collect.SingletonImmutableList using a local variable of type java.lang.Object[]. This is symptomatic of .class transformation tools that ignore local variable information.

Bug: 36902714
Bug: 37077388
Test: m -j ANDROID_COMPILE_WITH_JACK=false
Change-Id: I687fff179c9d264f788e89e18cf5875c5f0663fc
(cherry picked from commit 54033c62b5b9e911d54d509b812c8a2b224510b4)
diff --git a/Android.mk b/Android.mk
index 9602ab8..02ca05a 100644
--- a/Android.mk
+++ b/Android.mk
@@ -267,7 +267,12 @@
     java/com/android/dialer/proguard/proguard.flags \
     java/com/android/dialer/proguard/proguard_release.flags \
     java/com/android/incallui/answer/impl/proguard.flags
-LOCAL_PROGUARD_ENABLED := custom optimization
+LOCAL_PROGUARD_ENABLED := custom
+
+ifdef LOCAL_JACK_ENABLED
+# Bug: 37077388
+LOCAL_PROGUARD_ENABLED += optimization
+endif
 
 LOCAL_SDK_VERSION := current
 LOCAL_MODULE_TAGS := optional