contrib/jenkins.sh: speed up pylint by running multiple processes

Use multiple processes to speed up pylint.  Specifying -j0 will
auto-detect the number of processors available to use.

On AMD Ryzen 7 3700X this significantly reduces the exec time:

  $ time python -m pylint -j1 ... pySim *.py
  real    0m12.409s
  user    0m12.149s
  sys     0m0.136s

  $ time python -m pylint -j0 ... pySim *.py
  real    0m5.541s
  user    0m58.496s
  sys     0m1.213s

Change-Id: I76d1696c27ddcab358526f807c4a0a7f0d4c85d4
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index bdf1311..f5cf8a2 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -37,7 +37,7 @@
 #   pySim/utils.py:276: E0401: Unable to import 'Crypto.Cipher' (import-error)
 #   pySim/utils.py:277: E0401: Unable to import 'Crypto.Util.strxor' (import-error)
 pip install pylint==2.14.5 # FIXME: 2.15 is crashing, see OS#5668
-python -m pylint --errors-only \
+python -m pylint -j0 --errors-only \
 	--disable E1102 \
 	--disable E0401 \
 	--enable W0301 \