Summary:
This makes it easier for us to move the build to libc++, because
it allows build flags to be seamlessly used by the BCC build.

Test Plan: Jenkins

Reviewers: oazizi, yzhao, #engineering

Reviewed By: oazizi, yzhao, #engineering

Differential Revision: https://phab.corp.pixielabs.ai/D1044

GitOrigin-RevId: f8cf302795b7dab9b00a33fd72a1ca97cce607f2