use Release as default build type

CMakeLists.txt

@@ -39,6 +39,16 @@ enable_language(CXX)
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/cmake/Modules/" ${CMAKE_MODULE_PATH})
 
+set(default_build_type "Release")
+if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
+  message(STATUS "Setting build type to '${default_build_type}' as none was specified.")
+  set(CMAKE_BUILD_TYPE "${default_build_type}" CACHE
+      STRING "Choose the type of build." FORCE)
+  # Set the possible values of build type for cmake-gui
+  set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS
+    "Debug" "Release" "MinSizeRel" "RelWithDebInfo")
+endif()
+
 if (CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
   set(CMAKE_INSTALL_PREFIX "${CMAKE_CURRENT_LIST_DIR}" CACHE PATH "Install prefix" FORCE)
 endif()