Travis: mark MacOS builds as optional

MacOS support in Travis is flakey right now. MacOS build jobs
take a long time to start.

We have extensive checks for Linux and Windows, which should give
us confidence.

diff --git a/.travis.yml b/.travis.yml
index ba3d252..48cd0e2 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,6 +24,8 @@ compiler:
   - gcc
 
 matrix:
+  allow_failures:
+    - os: osx
   fast_finish: true
   include:
     # Additional build using Android NDK with android-cmake