Make --save-smt/--save-macaw options accept a directory to create files in

[RyanGlScott]

The test suites for the macaw-*-symbolic suite of packages define --save-smt/--save-macaw switches, which can be used to dump intermediate SMT queries and Macaw CFGs to text files under the /tmp directory for debugging purposes. In #411 (comment), @kquick observed that this isn't quite ideal, since generating these files in a global location like /tmp can mix them in with other runs of the test suite, possibly leading to users looking at the wrong files.

Instead, it would be better if --save-smt/--save-macaw each took a directory as an argument, dumping their contents to files contained in that directory. That way, the user can generate the files to a known location (e.g., the current directory). This would also make it easier to generate these files during CI and possibly save them as artifacts.

[sauclovian-g]

Also, on a multiuser/server machine dropping stuff with predictable names in /tmp (without taking precautions) is a bad idea and can lead to security advisories.