Revert "Remove desugar support"

This reverts commit bfad2c070c86d2a78eb730aaf75ac6b676405133.

Reason for revert: broke art veridex build

Change-Id: I0dcc34102ee18b054c2247ae0e2698aca645c667
diff --git a/core/config.mk b/core/config.mk
index 0920b56..6c062a6 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -570,7 +570,9 @@
 
 # Work around for b/68406220
 # This should match the soong version.
-USE_D8 := true
+ifndef USE_D8
+  USE_D8 := true
+endif
 
 # Default R8 behavior when USE_R8 is not specified.
 ifndef USE_R8
@@ -584,6 +586,7 @@
   AIDL := $(HOST_OUT_EXECUTABLES)/aidl
   AAPT := $(HOST_OUT_EXECUTABLES)/aapt
   AAPT2 := $(HOST_OUT_EXECUTABLES)/aapt2
+  DESUGAR := $(HOST_OUT_JAVA_LIBRARIES)/desugar.jar
   MAINDEXCLASSES := $(HOST_OUT_EXECUTABLES)/mainDexClasses
   SIGNAPK_JAR := $(HOST_OUT_JAVA_LIBRARIES)/signapk$(COMMON_JAVA_PACKAGE_SUFFIX)
   SIGNAPK_JNI_LIBRARY_PATH := $(HOST_OUT_SHARED_LIBRARIES)
@@ -593,6 +596,7 @@
   AIDL := $(prebuilt_build_tools_bin)/aidl
   AAPT := $(prebuilt_sdk_tools_bin)/aapt
   AAPT2 := $(prebuilt_sdk_tools_bin)/aapt2
+  DESUGAR := $(prebuilt_build_tools_jars)/desugar.jar
   MAINDEXCLASSES := $(prebuilt_sdk_tools)/mainDexClasses
   SIGNAPK_JAR := $(prebuilt_sdk_tools)/lib/signapk$(COMMON_JAVA_PACKAGE_SUFFIX)
   SIGNAPK_JNI_LIBRARY_PATH := $(prebuilt_sdk_tools)/$(HOST_OS)/lib64