add r to eng and userdebug builds

Change-Id: Ia52a4897e300568dad2c8c1c7af1fe228d058eaf
diff --git a/toolbox/Android.mk b/toolbox/Android.mk
index 76542a6..d7a675a 100644
--- a/toolbox/Android.mk
+++ b/toolbox/Android.mk
@@ -57,6 +57,10 @@
 	touch \
 	lsof
 
+ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))
+TOOLS += r
+endif
+
 LOCAL_SRC_FILES:= \
 	dynarray.c \
 	toolbox.c \