Remove unused $MD5SUM.

Test: treehugger
Change-Id: I63273b1602362a84beaf32d2260a0a4e35e6ef4d
diff --git a/core/config.mk b/core/config.mk
index 1d1aa6a..df56edb 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -119,6 +119,7 @@
   ARCH_X86_HAVE_SSSE3 \
 )
 $(KATI_obsolete_var PRODUCT_IOT)
+$(KATI_obsolete_var MD5SUM)
 
 # Used to force goals to build.  Only use for conditionally defined goals.
 .PHONY: FORCE
@@ -648,13 +649,6 @@
 # Path to tools.jar
 HOST_JDK_TOOLS_JAR := $(ANDROID_JAVA8_HOME)/lib/tools.jar
 
-# It's called md5 on Mac OS and md5sum on Linux
-ifeq ($(HOST_OS),darwin)
-MD5SUM:=md5 -q
-else
-MD5SUM:=md5sum
-endif
-
 APICHECK_COMMAND := $(JAVA) -Xmx4g -jar $(APICHECK) --no-banner --compatible-output=yes
 
 # Boolean variable determining if the whitelist for compatible properties is enabled