Use libpkgx semver

[mxcl]

Refs #24

[mxcl]

Failure because we’ve been setting rpath incorrectly on Linux for a while. Everything works with PKGX because we set the LD_LIBRARY_PATH on execution, but pkgm assumes that isn’t necessary (which is true, if rpaths are correct). This works on macOS since our rpaths are correct.

This only applies to local-installs since /usr/local installs have the libraries in a standard location.

edit: well ok, apparently not. I don’t understand why, /usr/local/lib/libssl.so.1.1 is there. I guess if you set the rpath explicitly the runtime linker stops looking in the normal places or something?