[llvm-libc] Fix missing virtual destructor

Summary: This patch adds a virtual destructor to the Command class.

Reviewers: sivachandra

Subscribers: mgorny, MaskRay, libc-commits

Tags: #libc-project

Differential Revision: https://reviews.llvm.org/D72253

GitOrigin-RevId: 3e1f3b164cc0b4be486eebf24cca79c9f9c8c1f7
3 files changed