fix travis build issue

This morning, I found that all the c++ build job related to "TOOLSET=asan" returns an error, even we try to rebuild the old jobs which already passed:

Debug w/ @springmeyer, we thought this is a new Travis error due to a new leak in node.js.

To fix this issue we need to add echo "leak:node::Start" >> ${SUPPRESSION_FILE} in scripts/sanitize.sh

diff --git a/scripts/sanitize.sh b/scripts/sanitize.sh
index 4168cca..28c9344 100755
--- a/scripts/sanitize.sh
+++ b/scripts/sanitize.sh
@@ -24,6 +24,7 @@ SUPPRESSION_FILE="/tmp/leak_suppressions.txt"
 echo "leak:__strdup" > ${SUPPRESSION_FILE}
 echo "leak:v8::internal" >> ${SUPPRESSION_FILE}
 echo "leak:node::CreateEnvironment" >> ${SUPPRESSION_FILE}
+echo "leak:node::Start" >> ${SUPPRESSION_FILE}
 echo "leak:node::Init" >> ${SUPPRESSION_FILE}
 export ASAN_SYMBOLIZER_PATH=$(pwd)/mason_packages/.link/bin/llvm-symbolizer
 export MSAN_SYMBOLIZER_PATH=$(pwd)/mason_packages/.link/bin/llvm-symbolizer

OR see this PR https://github.com/mapbox/node-cpp-skel/pull/156/files.

This will fix the issue.

cc w/ @mapbox/maps-api @flippmoke @mapsam @millzpaugh

Start with scripts/sanitize.sh and the Travis jobs using TOOLSET=asan. Compare the sanitizer suppression entries with the referenced node-cpp-skel pull request, then rerun or inspect the affected C++ ASAN build; done means the ASAN jobs complete without the reported Node.js leak failure.