Statically link libminijail to debuggerd_test.

We do not install a 32-bit version of libminijail to 64/32 devices,
which means that "atest -a debuggerd_test" always fails on 32-bit.
Fix it by statically linking libminijail.

Change-Id: I1e5610d1353b4f5b718c1259825421c0c07d7c24