> With this patch applied, I can set the environment variable EMACS_ENV
> to ">PATH>${msys2_root}/mingw64/bin", and have that directory appended
> to the PATH but only in the environment of the runemacs process.  That
> environment is inherited by the emacs process, so I can allow Emacs to
> find the libraries it needs in order to run without copying them to
> the Emacs installation directory and without altering the PATH for my
> user account.

Why not simply have a myrunemacs.bat

@echo off

setlocal

set PATH=%PATH;/your/path/to/mingw64/bin

runemacs %*

endlocal

??