build: allow Jenkins to specify number of waf build jobs

Change-Id: Idb58cdf572ab6a240300c9febbb2cfe9638e8233
diff --git a/.jenkins.d/10-build.sh b/.jenkins.d/10-build.sh
index 8af1fc4..f25f060 100755
--- a/.jenkins.d/10-build.sh
+++ b/.jenkins.d/10-build.sh
@@ -14,11 +14,11 @@
 find . -name '*.pyc' | sudo xargs rm -f
 
 # Configure/build in debug mode
-./waf -j1 configure -d debug --enable-modules=ndnSIM --enable-examples --enable-tests $EXTRA_FLAGS
-./waf -j1 build
+./waf -j${WAF_JOBS:-1} configure -d debug --enable-modules=ndnSIM --enable-examples --enable-tests $EXTRA_FLAGS
+./waf -j${WAF_JOBS:-1}  build
 
 # Install
-sudo ./waf -j1 install
+sudo ./waf -j${WAF_JOBS:-1} install
 
 if has Linux $NODE_LABELS; then
     sudo ldconfig