How to install an old port from the binary archive?

[Jimmy Yuen Ho Wong]

Hi,

The latest gcc11 port has disabled the jit and thus broke emacs-devel. I 
am trying to install an older version of gcc11 from the default binary 
archive. I can see the tarball clearly still exists on 
`https://packages.macports.org/libgcc11/`, but `port -b install` from a 
local ports dir complains about `Error: Failed to archivefetch libgcc11: 
Binary-only mode requested with no usable archive sites configured`, 
what gives?

Jimmy