build: allow test-ci to run tests in parallel

Run tests in parallel if the environment variable JOBS
(which should contain a number of parallel jobs) is set.

PR-URL: nodejs#6208
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

Makefile

@@ -8,9 +8,12 @@ PREFIX ?= /usr/local
 FLAKY_TESTS ?= run
 TEST_CI_ARGS ?=
 STAGINGSERVER ?= node-www
-
 OSTYPE := $(shell uname -s | tr '[A-Z]' '[a-z]')
 
+ifdef JOBS
+  PARALLEL_ARGS = -j $(JOBS)
+endif
+
 ifdef QUICKCHECK
   QUICKCHECK_ARG := --quickcheck
 endif
@@ -168,7 +171,8 @@ test-all-valgrind: test-build
 	$(PYTHON) tools/test.py --mode=debug,release --valgrind
 
 test-ci: | build-addons
-	$(PYTHON) tools/test.py -p tap --logfile test.tap --mode=release --flaky-tests=$(FLAKY_TESTS) \
+	$(PYTHON) tools/test.py $(PARALLEL_ARGS) -p tap --logfile test.tap \
+		--mode=release --flaky-tests=$(FLAKY_TESTS) \
 		$(TEST_CI_ARGS) addons message parallel sequential
 
 test-release: test-build
@@ -607,8 +611,9 @@ jslint:
 	  tools/eslint-rules tools/jslint.js
 
 jslint-ci:
-	$(NODE) tools/jslint.js -f tap -o test-eslint.tap benchmark lib src test \
-	  tools/doc tools/eslint-rules tools/jslint.js
+	$(NODE) tools/jslint.js $(PARALLEL_ARGS) -f tap -o test-eslint.tap \
+		benchmark lib src test tools/doc \
+		tools/eslint-rules tools/jslint.js
 
 CPPLINT_EXCLUDE ?=
 CPPLINT_EXCLUDE += src/node_lttng.cc