Commits
François Saint-Jacques authored and Wes McKinney committed e648a762586
ARROW-4672: [CI] Fix clang-7 build entry The current entry defines the `CC` and `CXX` variables in the `env` section. The 2 variables are then redefined by travis with the `language: cpp` directive. This ensure that the variables are not overwritten. Author: François Saint-Jacques <fsaintjacques@gmail.com> Closes #3769 from fsaintjacques/ARROW-4672-travis-clang-7 and squashes the following commits: 455cd65a <François Saint-Jacques> ARROW-4672: Fix clang-7 build entry