CPack/WiX: Add the build directory to IncludeSearchPaths for wix.exe

In commit f2134169f6 (WiX: Add the build directory to IncludeSearchPaths
for candle.exe, 2018-07-06, v3.13.0-rc1~318^2) we implemented this for
WiX v3 with `candle.exe`.  Use the same mechanism for Wix v4 and upwards
for `wix.exe`.
1 file changed