Rename r8 to r8-compat-proguard

Test: USE_R8=false USE_D8=true m -j32 && USE_R8=true USE_D8=true m -j32

Change-Id: I2610340cf75f8db5920e33fac542f0dcf294ce29
diff --git a/core/config.mk b/core/config.mk
index f54ea5f..c993c1b 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -546,7 +546,7 @@
   ZIPALIGN := $(prebuilt_sdk_tools_bin)/zipalign
 endif # TARGET_BUILD_APPS || TARGET_BUILD_PDK
 
-R8_COMPAT_PROGUARD_JAR := prebuilts/r8/compatproguard-master.jar
+R8_COMPAT_PROGUARD := $(HOST_OUT_EXECUTABLES)/r8-compat-proguard
 
 ifeq (,$(TARGET_BUILD_APPS))
   # Use RenderScript prebuilts for unbundled builds but not PDK builds