Pass a real flag to mkdir instead of a pretend one

Change-Id: I96296c79c6c6ab091cb94a44b1a2e235474db534
Reviewed-on: http://gerrit.dmdirc.com/1641
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>

dynamicProperties.sh

 else
 	# Make sure target exists.
 	if [ ! -e "${TARGET}" ]; then
-		mkdir -P `dirname "${TARGET}"`
+		mkdir -p `dirname "${TARGET}"`
 		touch "${TARGET}"
 	fi;