[Cmake] Issues and new ideas

[Cross, Geoff (CRD)]

> With the notion of IGNORE there isn't as much need for a HAS_LIB
> value, I thought that was the motivation for adding IGNORE. The above
> code would reduce to
> 
> FIND_LIBRARY(JPEG_LIBRARY jpeg path path...)
> 
> IF (JPEG_LIBRARY)
>    do something with it
> ENDIF (JPEG_LIBRARY)
> 
> IF would only execute if JPEG_LIBRARY was (not (NOTFOUND || IGNORE))
> Likewise FIND_LIBRARY would only search for the library when
> JPEG_LIBRARY was NOTFOUND (or completely empty)

But it looks like FIND_LIBRARY will do the search unless JPEG_LIBRARY is "NOTFOUND".  If it were
IGNORE, off it would go and start searching.

Geoff.