Summary: Change default compiler to be gcc-10. It was set to gcc-9.3 before.

Test Plan: Jenkins

Reviewers: michelle, oazizi, #engineering

Reviewed By: oazizi, #engineering

Differential Revision: https://phab.corp.pixielabs.ai/D5695

GitOrigin-RevId: 9b6df9c1313b0197dbee1aa4e1c968670eed0d5d