ASan: Add asan_static to build

This is a partial fix for building with -DWITH_ASAN.

Reviewed by: Fangrui Song, dim, emaste
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D42388

(cherry picked from commit 5c783a0b2826d1c6bbaa7d4b01a46d1dcdb39e8c)