ktest.pl: Have -D option work without a space

Allow -DBUILD_TYPE=boot work the same as -D BUILD_TYPE=boot just like
normal single character option does in most applications.

Cc: "John Warthog9 Hawley" <warthog9@kernel.org>
Cc: Dhaval Giani <dhaval.giani@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/20250718202053.567246162@kernel.org


Signed-off-by: Steven Rostedt <rostedt@goodmis.org>