CleanSpec: Clean up $(PRODUCT_OUT)/recovery/root/sdcard.

Incremental build going across CL in [1] needs to remove the old
symlink to avoid hitting mkdir error.

[1]: commit 3f56a330412b56212acc5a9ed19b747c8943b7f2

Change-Id: Iff62ed55eb2782ba3e1e9b6de39a691de2427384
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 64d84e3..19cb651 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -371,6 +371,9 @@
 
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/build.prop)
 
+# $(PRODUCT_OUT)/recovery/root/sdcard goes from symlink to folder.
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/recovery/root/sdcard)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************