cmake: set default CMAKE_BUILD_TYPE to Release

this matches configure

Change-Id: I95f6f073b9dba1ae2c2b48b6c89a762277777dfe

CMakeLists.txt

@@ -12,7 +12,7 @@ cmake_minimum_required(VERSION 3.5)
 
 if (NOT EMSCRIPTEN)
   if (NOT CMAKE_BUILD_TYPE)
-    set(CMAKE_BUILD_TYPE "RelWithDebInfo" CACHE
+    set(CMAKE_BUILD_TYPE "Release" CACHE
       "Build type: Debug, Release, RelWithDebInfo or MinSizeRel" STRING FORCE)
   endif ()
 endif ()