If msys2 bash is set as the DefaultShell for the Win10 OpenSSH server,
there is no way to pass -l to make it a login shell, so /etc/profile is
not sourced, PATH is not set, and the bashrc produces errors.
Detect this case in /etc/bash.bashrc, by checking for the SSH_CONNECTION
environment variable and PATH not having msys2 elements, and source
/etc/profile.
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