.travis.yml: use several different OSX versions

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>

diff --git a/.travis.yml b/.travis.yml
index 026a05f26e0c901c6cffc82deb52c1d3963cbde5..02f641b6a4dd3be39bbc3721258a84db1e8c7e2e 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,16 @@
 os:
  - osx
 
+osx_image:
+  # MacOS X 10.15.4
+  - xcode11.5
+  # MacOS X 10.14.6
+  - xcode11.3
+  # MacOS X 10.13
+  - xcode10.1
+  # MacOS X 10.13, Default
+  - xcode9.4
+
 language: c
 compiler:
   - clang