Remove build variant "tests"

Bug: 5368571
Now we have a phony target "tests" instead.
The target can be built in any other build variant (eg userdebug).
For example, "make PRODUCT-full-userdebug tests dist" will build and
put the *-test-* zip file in the dist dir.
The "tests" target will include all modules tagged as "tests" in
addition to other modules in specific target out directories.

Change-Id: I8383097380d8e6846c3e2107d6dd5f68788cfc39
diff --git a/core/main.mk b/core/main.mk
index e5c1b65..d86783b 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -232,8 +232,8 @@
 ifneq ($(filter user userdebug eng,$(MAKECMDGOALS)),)
 $(info ***************************************************************)
 $(info ***************************************************************)
-$(info Do not pass '$(filter user userdebug eng tests,$(MAKECMDGOALS))' on \
-		the make command line.)
+$(info Do not pass '$(filter user userdebug eng,$(MAKECMDGOALS))' on \
+       the make command line.)
 $(info Set TARGET_BUILD_VARIANT in buildspec.mk, or use lunch or)
 $(info choosecombo.)
 $(info ***************************************************************)
@@ -345,12 +345,6 @@
 endif
 endif
 
-## tests ##
-
-ifeq ($(TARGET_BUILD_VARIANT),tests)
-tags_to_install := debug eng tests
-endif
-
 ## sdk ##
 
 ifdef is_sdk_build