[R-pkg-devel] VignetteBuilder field

Assume an R package `myPackage` that contains the folder `vignettes`, in 
which the TEX-file `PACViR_Vignette.tex` and two image files 
(`image1.pdf` and `image2.pdf`) are located. The TEX-file compiles 
nicely without the need to use Sweave or knitr.

Upon testing the package for submission to CRAN via `R CMD check PACViR 
--as-cran`, I receive the following NOTES, which appear to prevent CRAN 
from accepting my package:


Flavor: r-devel-windows-ix86+x86_64
Check: files in 'vignettes', Result: NOTE
   Package has no Sweave vignette sources and no VignetteBuilder field.

Flavor: r-devel-linux-x86_64-debian-gcc
Check: files in ???vignettes???, Result: NOTE
   Package has no Sweave vignette sources and no VignetteBuilder field.


What is needed to address this issue? Do I need to specify a 
`VignetteBuilder` somewhere?