[PATCH] travis: Add LLVM-8 build

Runtimes OpenCL
#1

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

#2

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

ping.

#3

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

LGTM.