Travis: explicitly set compiler to clang on OSX

diff --git a/.travis.yml b/.travis.yml
index 5547cb3..ee6931f 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,6 +12,7 @@ matrix:
   include:
     - os: osx
       osx_image: xcode10.1
+      compiler: clang
     - os: linux
       dist: xenial
       compiler: clang