Ensure that the R8 minification map (ProGuard dictionary) file exists

R8 no longer outputs an empty map file when minification
(obfuscation) is turned off.

Test: m -j PRODUCT-aosp_x86-eng
Change-Id: I3bd3f2900225dca05a972f46a3b882041e17ba49
diff --git a/core/definitions.mk b/core/definitions.mk
index d36e7f0..e45cb01 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -2915,12 +2915,14 @@
 ###########################################################
 define transform-jar-to-dex-r8
 @echo R8: $@
+$(hide) rm -f $(PRIVATE_PROGUARD_DICTIONARY)
 $(hide) $(R8_COMPAT_PROGUARD) -injars '$<' \
     --min-api $(PRIVATE_MIN_SDK_VERSION) \
     --force-proguard-compatibility --output $(subst classes.dex,,$@) \
     $(PRIVATE_PROGUARD_FLAGS) \
     $(addprefix -injars , $(PRIVATE_EXTRA_INPUT_JAR)) \
     $(PRIVATE_DX_FLAGS)
+$(hide) touch $(PRIVATE_PROGUARD_DICTIONARY)
 endef
 
 ###########################################################