YouCompleteMe workaround: explicitly include system include dirs

This patch is a workaround for
https://github.com/Valloric/YouCompleteMe/issues/303

It fixes various issues where standard headers cannot be found, such as:
https://groups.google.com/a/google.com/d/msg/ycm-users/TF9dqx0G0N8/bUQPR0jON80J

Review URL: https://codereview.chromium.org/842053003

Cr-Commit-Position: refs/heads/master@{#312363}
1 file changed