cargo vendor 🚚 on - remove _build from version control Summary: every time I build locally, the _build folder gets created which should not be checked in to version control. this creates many files and disrupts my development. this change makes hg ignore that directory. faq: [why not .hgignore?](https://fb.workplace.com/groups/sourcecontrolteam/permalink/1584634468324560/) Reviewed By: grievejia Differential Revision: D54199253 fbshipit-source-id: 571f241470573fc434d4df2777e9cb32990bab72

cargo vendor 🚚 on - remove _build from version control Summary: every time I build locally, the _build folder gets created which should not be checked in to version control. this creates many files and disrupts my development. this change makes hg ignore that directory. faq: [why not .hgignore?](https://fb.workplace.com/groups/sourcecontrolteam/permalink/1584634468324560/) Reviewed By: grievejia Differential Revision: D54199253 fbshipit-source-id: 571f241470573fc434d4df2777e9cb32990bab72 #92