travis: Add LLVM 9 build

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

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@373047 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed