Cannot build on macOS with arm clips

[vibhoothi]

Looks like our build is broken due to an upstream issue of git2
rust-lang/git2-rs#830

What should we do?

Build error logs

  = note: Undefined symbols for architecture arm64:
            "_iconv", referenced from:
                _git_fs_path_iconv in liblibgit2_sys-c4b10ec3554a20a0.rlib(fs_path.o)
               (maybe you meant: _git_fs_path_iconv, _git_fs_path_iconv_clear , _git_fs_path_iconv_init_precompose )
            "_iconv_close", referenced from:
                _git_fs_path_iconv_clear in liblibgit2_sys-c4b10ec3554a20a0.rlib(fs_path.o)
            "_iconv_open", referenced from:
                _git_fs_path_iconv_init_precompose in liblibgit2_sys-c4b10ec3554a20a0.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 `rav1e` (build script) due to previous error

[lukaso]

This issue is being tracked (and has been worked around) in https://trac.macports.org/ticket/68026