Link libcrypto in host unit tests for libavb

libavb is moving to use boringssl for crypto operations in user space
rather than using its own implementation. Link with libcrypto to
resolved the new dependencies.

Test: atest --host --host-unit-test-only --test-mapping system/core/fs_mgr/libfs_avb
Bug: 185329132
Change-Id: I412f4ef677aa6e29c5b67ffe5e3e8377640a2847