Previously libsnark would try to build libgtest if /usr/src/gtest
exists on the build machine. This caused issues because the
version of libgtest in /usr/src isn't necessarily the same as
the one that the rest of zcash's gtests were built with.
This fixes the way arguments were passed to security-check, and also
a typo in how BIND_NOW was being searched for in a list.
Also fix how symbol-check is invoked although that script isn't
currently used.
syd