Limit Jenkins builder concurrency to 3
diff --git a/tools/jenkins/run_jenkins.sh b/tools/jenkins/run_jenkins.sh
index 84b4ea5..15603c2 100755
--- a/tools/jenkins/run_jenkins.sh
+++ b/tools/jenkins/run_jenkins.sh
@@ -54,7 +54,7 @@
 then
   echo "building $language on Linux"
 
-  ./tools/run_tests/run_tests.py --use_docker -t -l $language -c $config -x report.xml $@ || TESTS_FAILED="true"
+  ./tools/run_tests/run_tests.py --use_docker -t -l $language -c $config -x report.xml -j 3 $@ || TESTS_FAILED="true"
 
 elif [ "$platform" == "windows" ]
 then
@@ -63,19 +63,19 @@
   # Prevent msbuild from picking up "platform" env variable, which would break the build
   unset platform
 
-  python tools/run_tests/run_tests.py -t -l $language -c $config -x report.xml $@ || TESTS_FAILED="true"
+  python tools/run_tests/run_tests.py -t -l $language -c $config -x report.xml -j 3 $@ || TESTS_FAILED="true"
 
 elif [ "$platform" == "macos" ]
 then
   echo "building $language on MacOS"
 
-  ./tools/run_tests/run_tests.py -t -l $language -c $config -x report.xml $@ || TESTS_FAILED="true"
+  ./tools/run_tests/run_tests.py -t -l $language -c $config -x report.xml -j 3 $@ || TESTS_FAILED="true"
 
 elif [ "$platform" == "freebsd" ]
 then
   echo "building $language on FreeBSD"
 
-  MAKE=gmake ./tools/run_tests/run_tests.py -t -l $language -c $config -x report.xml $@ || TESTS_FAILED="true"
+  MAKE=gmake ./tools/run_tests/run_tests.py -t -l $language -c $config -x report.xml -j 3 $@ || TESTS_FAILED="true"
 
 else
   echo "Unknown platform $platform"