cmake: make incompatible pointer types a hard error

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
5 jobs for pointer-fix in 3 minutes and 25 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Container
passed #867286
debian

00:00:24

 
  Build
passed #867287
build

00:02:00

passed #867288
py.test

00:00:54

passed #867289
tox

00:03:00

 
  External
failed continuous-integration/appveyor/branch