[BUGFIX] cli dispatcher throws notice on windows systems

In the CLI interface (cli_dispatch.phpsh) the server variable
$_SERVER['PWD'] is used which doesn't exists on windows
systems. PHP throws a notice, because the script doesn't check the
existence of the variable.

Change-Id: I425c48a7bd5a4e6fa9c86cc6e4dcae58493fd625
Fixes: #20392
Releases: 4.7, 4.5
Reviewed-on: https://review.typo3.org/19772
Reviewed-by: Ernesto Baschny
Tested-by: Ernesto Baschny