Add dependencies for files in LOCAL_PROGUARD_FLAGS

Do this by introducing a new LOCAL_PROGUARD_FLAGS_DEPS variable that we
can modify anytime we add a file reference to LOCAL_PROGUARD_FLAGS.

An alternative would have been to switch to LOCAL_PROGUARD_FLAG_FILES,
but that would have been much harder to ensure the same command line
ordering.

Bug: 130111713
Test: treehugger
Change-Id: If367197b30d563e0796f0cafa00be1f275f2c406
diff --git a/core/java_library.mk b/core/java_library.mk
index 34e4874..4734eaf 100644
--- a/core/java_library.mk
+++ b/core/java_library.mk
@@ -44,6 +44,7 @@
 LOCAL_STATIC_JAVA_LIBRARIES += jacocoagent
 # Exclude jacoco classes from proguard
 LOCAL_PROGUARD_FLAGS += -include $(BUILD_SYSTEM)/proguard.jacoco.flags
+LOCAL_PROGUARD_FLAGS_DEPS += $(BUILD_SYSTEM)/proguard.jacoco.flags
 endif # LOCAL_EMMA_INSTRUMENT
 endif # EMMA_INSTRUMENT_STATIC
 else