buildtools: fix all drivers disabled on Windows

buildtools: fix all drivers disabled on Windows

buildtools/list-dir-globs.py printed paths with OS directory separator,
which is "/" on Unices and "\" on Windows, while Meson code always
expected "/". This resulted in all drivers being disabled on Windows.

Replace "\" with "/" in script output. Forward slash is a valid,
although non-default, separator on Windows, so no paths can be broken
by this substitution.

Fixes: ab9407c3addd ("build: allow using wildcards to disable drivers")
Cc: stable@dpdk.org
Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>