trusty: fuzz: Link libtrusty_test statically

Simplifies development flow because libtrusty_test.so doesn't need to be
pushed with the fuzzer.

Bug: 171750250
Test: m trusty_gatekeeper_fuzzer && adb sync data && \
adb shell /data/fuzz/arm64/trusty_gatekeeper_fuzzer/trusty_gatekeeper_fuzzer
Change-Id: I7c83b5784ede4881dcd9c2dd33c97bf49fcde6ff

Change-Id: Iba60f03000bfca15b00e484ef3a168604c65554a