texinfo-dummy-native: Fix dummy scripts failing when paths contain capital Es

This was an issue in the command-line argument parsing. It was the cause of
the bug reported on the OE-core mailing list by Denys Dmytriyenko.

Signed-off-by: Max Eliaser <max.eliaser@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>