ktest.pl: Always display BUILD_DIR and OUTPUT_DIR at the start of tests

As ktest.pl can run in various different directories, to make sure the
test is running in the proper directory with the proper source and proper
destination directory, display the content of BUILD_DIR and OUTPUT_DIR at
the start of every test.

This can be helpful for the test runner to stop the test if a test is
running in the wrong location instead of finding out after the test has
completed.

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/20250718202053.898022631@kernel.org


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