ci: preserve PATH when running waf under sudo

Change-Id: Ideb6f9d4ec3d92af134b923b9abafc952ee868e6
Refs: #4186
diff --git a/.jenkins.d/01-ndn-cxx.sh b/.jenkins.d/01-ndn-cxx.sh
index 7a42b5a..c9e2a63 100755
--- a/.jenkins.d/01-ndn-cxx.sh
+++ b/.jenkins.d/01-ndn-cxx.sh
@@ -44,7 +44,7 @@
 
 ./waf configure --color=yes --enable-shared --disable-static --without-osx-keychain
 ./waf build --color=yes -j${WAF_JOBS:-1}
-sudo ./waf install --color=yes
+sudo env "PATH=$PATH" ./waf install --color=yes
 
 popd >/dev/null
 popd >/dev/null