fix: linker warning

[dabfleming]

Using v2 I get a persistent warning when running tests:

ld: warning: directory not found for option '-L/opt/pact/lib'

When I poked around I discovered I didn't have any pact tooling installed under /opt/pact. I'm assuming this was left over from previous stuff but is not used by the go based installer?

All I seem to get after installing is /usr/local/lib/libpact_ffi.dylib

[mefellows]

I had plans to allow the libraries to be installed in multiple places. /usr/local/lib is not always accessible, so having backups for those users with locked down machines is nice. But let's stick with this and see what happens when it expands further into the wild - thanks.