Fix setup scripts for Mac M1/MacPort configuration

[abey79]

What

This PR includes two minor changes needed to for the setup_dev.sh script to complete on my M1 machine with MacPorts:

1. Add MacPorts in the list of supported package managers.
2. Add --locked flag when installing cargo-deny

Without --locked, I would get the following error:

 = note: Undefined symbols for architecture arm64:
            "_iconv", referenced from:
                _git_fs_path_iconv in liblibgit2_sys-855562e07780fd1f.rlib(fs_path.o)
               (maybe you meant: _git_fs_path_iconv_clear, _git_fs_path_iconv_init_precompose , _git_fs_path_iconv )
            "_iconv_close", referenced from:
                _git_fs_path_direach in liblibgit2_sys-855562e07780fd1f.rlib(fs_path.o)
                _git_fs_path_iconv_clear in liblibgit2_sys-855562e07780fd1f.rlib(fs_path.o)
                _git_fs_path_diriter_free in liblibgit2_sys-855562e07780fd1f.rlib(fs_path.o)
                _git_fs_path_dirload in liblibgit2_sys-855562e07780fd1f.rlib(fs_path.o)
            "_iconv_open", referenced from:
                _git_fs_path_direach in liblibgit2_sys-855562e07780fd1f.rlib(fs_path.o)
                _git_fs_path_iconv_init_precompose in liblibgit2_sys-855562e07780fd1f.rlib(fs_path.o)
                _git_fs_path_diriter_init in liblibgit2_sys-855562e07780fd1f.rlib(fs_path.o)
          ld: symbol(s) not found for architecture arm64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)


error: could not compile `cargo-deny` due to previous error

I haven't investigated why this is so, but the cargo-deny project always includes --locked in its installation instructions.

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
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[jleibs]

Thanks for the improvements!