Add build goal "tests".

Bug: 5368571
The phony build goal "tests" will eventually replace the build variant
tests.

Change-Id: Ia656f2cf2260feeaa8fa32e9221b7f9ce0990262
diff --git a/core/main.mk b/core/main.mk
index 5604df2..0084a0b 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -183,7 +183,7 @@
 # Bring in dex_preopt.mk
 include $(BUILD_SYSTEM)/dex_preopt.mk
 
-ifneq ($(filter eng user userdebug tests,$(MAKECMDGOALS)),)
+ifneq ($(filter eng user userdebug,$(MAKECMDGOALS)),)
 $(info ***************************************************************)
 $(info ***************************************************************)
 $(info Don't pass '$(filter eng user userdebug tests,$(MAKECMDGOALS))' on \
@@ -797,8 +797,7 @@
 endif # droid in $(MAKECMDGOALS)
 
 
-.PHONY: droid tests
-tests: droidcore
+.PHONY: droid
 
 # phony target that include any targets in $(ALL_MODULES)
 .PHONY: all_modules