Only set REALM_DEBUG for debug builds

CMake/CompilerFlags.cmake

@@ -1,8 +1,8 @@
 set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_STANDARD_REQUIRED on)
 set(CMAKE_CXX_EXTENSIONS off)
-set(CMAKE_BUILD_TYPE CACHE STRING Debug)
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -DREALM_HAVE_CONFIG -DREALM_DEBUG")
+add_compile_options(-Wall -DREALM_HAVE_CONFIG)
+add_compile_options("$<$<CONFIG:DEBUG>:-DREALM_DEBUG>")
 
 if(${CMAKE_GENERATOR} STREQUAL "Ninja")
     if(${CMAKE_CXX_COMPILER_ID} STREQUAL "Clang")

CMakeLists.txt

@@ -1,3 +1,4 @@
+set(CMAKE_BUILD_TYPE Debug CACHE STRING "")
 project(realm-object-store)
 
 cmake_minimum_required(VERSION 3.2.0)