The JTREG_VERBOSE and JCK_VERBOSE variables in langtools/test/Makefile set their default values with "=". This ends up overriding any settings in environment variables. "?=" would be a better operator, allowing user settings to be preferred. (Notably, this allows the setting to be passed down from the top-level makefile with target "test", since that script removes the variable from the command line when it makes a recursive 'make' call using "MAKEFLAGS=".)

It's not clear how the TEST_SELECTION variable is intended to be used. Most targets -- all, jtreg, javac, etc. -- override it. It sticks when calling 'jtreg-tests' directly, but it's unclear whether this is intended to be "public" usage, since it skips the cleanup and summary steps that other targets get. Two suggestions:
- Allow the 'jtreg' target to defer to the user's setting of TEST_SELECTION
- Re-use TEST_SELECTION as a way to control JCK tests

The TESTDIRS and DEFAULT_TESTDIRS variables are apparently unused (no uses appear in a grep of langtools), and just cause confusion. They should be deleted.