better support for Win10 OpenSSH server (#1375)

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.

filesystem/bash.bashrc

@@ -15,6 +15,11 @@
 # If not running interactively, don't do anything
 [[ "$-" != *i* ]] && return
 
+# If started from sshd, make sure profile is sourced
+if [[ -n "$SSH_CONNECTION" ]] && [[ "$PATH" != *:/usr/bin* ]]; then
+    source /etc/profile
+fi
+
 # Warnings
 unset _warning_found
 for _warning_prefix in '' ${MINGW_PREFIX}; do