Link libcrypto dynamically for recovery unit tests.

Tested by running recovery_unit_test as described in
https://android.googlesource.com/platform/bootable/recovery/+/refs/heads/master/README.md

Attempted to build and boot a recovery image with the
same change to confirm it still works, but
m recoveryimage-nodeps
fails for me.

Bug: 140940227
Test: See above
Change-Id: I00545968a0e5684823e505f2ddbe7e993319b5d4