Fix curl use under cygwin and possibly other curl scenarios.

update-minetest-linux64.sh

@@ -28,6 +28,10 @@ else
     fi
     MT_BASH_RC_URL=https://raw.githubusercontent.com/poikilos/EnlivenMinetest/master/$MT_BASH_RC_NAME
     curl $MT_BASH_RC_URL -o "$MT_BASH_RC_PATH"
+    if [ $? -ne 0 ]; then
+        # This is necessary on cygwin for some reason.
+        curl $MT_BASH_RC_URL > "$MT_BASH_RC_PATH"
+    fi
     if [ $? -ne 0 ]; then
         echo
         echo "ERROR: Downloading $MT_BASH_RC_URL to $MT_BASH_RC_PATH failed."