RFR: JDK-8159186: jdk/test/Makefile: allow users to set verbosity

[Dan Smith]

I'd like to make a simple tweak to jdk/test/Makefile in order to support control over the "-v" verbosity option sent to jtreg.  'langtools/test/Makefile' has supported a similar "JTREG_VERBOSE" variable for awhile now.

(Would it be nice to align the test-running infrastructure for langtools and jdk more closely, and maybe integrate better into the rest of the Makefile setup?  Sure, yes.  Totally out of scope for what I'm doing here, though, which is just trying to eliminate a small pain point.)

# HG changeset patch
# Parent b803887ddddc681a9cfa067a1a4ccab70c465a53
diff -r b803887ddddc -r b629baacaa5b test/Makefile
--- a/test/Makefile	Thu Jun 02 15:36:15 2016 +0300
+++ b/test/Makefile	Wed Jun 08 15:20:04 2016 -0600
@@ -316,8 +316,9 @@
 # Always turn on assertions
 JTREG_ASSERT_OPTION = -ea -esa
 JTREG_BASIC_OPTIONS += $(JTREG_ASSERT_OPTION)
-# Report details on all failed or error tests, times too
-JTREG_BASIC_OPTIONS += -v:fail,error,time
+# jtreg verbosity setting
+JTREG_VERBOSE ?= fail,error,time
+JTREG_BASIC_OPTIONS += $(if $(JTREG_VERBOSE),-v:$(JTREG_VERBOSE))
 # Retain all files for failing tests
 JTREG_BASIC_OPTIONS += -retain:fail,error
 # Ignore tests are not run and completely silent about it

Can I get a reviewer's approval?

—Dan