buildtools: enable header includes check on Windows

buildtools: enable header includes check on Windows

Independent header compilation test (chkincs) was disabled on Windows.
The comment stated that the shebang line in the generator script was not
working. Meson 0.57.0, currently recommended for Windows, successfully
parses that line and invokes the script. Remove the OS restriction
as its reason no longer applies.

Fixes: 05050ac4ce99 ("build: add header includes check")

Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>