cmake: Fix some spurious copy'n'paste code in inject module.

Which was causing ninja-build to issue a warning.
dxgiretrace: Ensure checker pattern initialisation constants are unsigned.

To silence recent gcc version.
thirdparty/less: Remove.

I doubt any Windows user is relying on the bundled less.  I haven't used
it myself as much as I imagined.  And one can always install it
separately.