ci: auto-detect the OS instead of relying on NODE_LABELS

And remove WAF_JOBS: waf already defaults to the number of available
CPUs, which is appropriate in most cases, and we can always use the
built-in JOBS variable to override it where necessary.

Change-Id: Id132b9ef8467a563694222ccc64a676cdc076e17
diff --git a/.jenkins.d/20-tests.sh b/.jenkins.d/20-tests.sh
index 81c00b1..ab14284 100755
--- a/.jenkins.d/20-tests.sh
+++ b/.jenkins.d/20-tests.sh
@@ -1,8 +1,5 @@
 #!/usr/bin/env bash
-set -ex
-
-# Prepare environment
-rm -rf ~/.ndn
+set -eo pipefail
 
 # https://github.com/google/sanitizers/wiki/AddressSanitizerFlags
 ASAN_OPTIONS="color=always"
@@ -14,10 +11,16 @@
 ASAN_OPTIONS+=":strip_path_prefix=${PWD}/"
 export ASAN_OPTIONS
 
+# https://www.boost.org/doc/libs/release/libs/test/doc/html/boost_test/runtime_config/summary.html
 export BOOST_TEST_BUILD_INFO=1
 export BOOST_TEST_COLOR_OUTPUT=1
 export BOOST_TEST_DETECT_MEMORY_LEAK=0
 export BOOST_TEST_LOGGER=HRF,test_suite,stdout:XML,all,build/xunit-log.xml
 
+set -x
+
+# Prepare environment
+rm -rf ~/.ndn
+
 # Run unit tests
 ./build/unit-tests