Bump minimum required CMake version to 2.8.12.

CMake 2.8.12 added support for target_include_directories(), among other features, and we would like to use it.
2016-05-04 13:06:15 -04:00 · 2016-05-04 13:06:15 -04:00 · 045e02af75
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 2.8.12)

 enable_testing()