Note that if a plugin and the main program have any packages in common, the build-hash (Go binaries include a hash for each included package) must be identical

Note that if a plugin and the main program have any packages in common, the build-hash (Go binaries include a hash for each included package) must be identical between the program and the plugin. If the hashes don't match, then the program's `plugin.Open(…)` call will return an error. So if there is a package in common such that an implementation change could cause something like a cgshape change, well the cgshape change won't matter since any implementation change will change the package's build-hash. And so everything will need recompiled anyway, regardless of whether the cgshape changed or not.