cmake: Add dolphin_compile_definitions function

This is similar to add_definitions, but supports generator expressions.
It also has an optional argument to add only to Debug or Release
configurations.

CMakeLists.txt

@@ -79,6 +79,7 @@ list(APPEND CMAKE_MODULE_PATH
 # Support functions
 include(CheckAndAddFlag)
 include(CheckCCompilerFlag)
+include(DolphinCompileDefinitions)
 
 # Libraries to link
 set(LIBS)
@@ -193,6 +194,7 @@ endif()
 
 if(CMAKE_C_COMPILER_ID MATCHES "MSVC")
 	check_and_add_flag(EXCEPTIONS /EHsc)
+	dolphin_compile_definitions(-D_DEBUG DEBUG_ONLY)
 
 	# Only MSBuild needs this, other generators will compile one file at a time
 	if(CMAKE_GENERATOR MATCHES "Visual Studio")
@@ -226,6 +228,8 @@ else()
 	check_and_add_flag(VISIBILITY_HIDDEN -fvisibility=hidden)
 
 	check_and_add_flag(FOMIT_FRAME_POINTER -fomit-frame-pointer RELEASE_ONLY)
+
+	dolphin_compile_definitions(_DEBUG DEBUG_ONLY)
 	check_and_add_flag(GGDB -ggdb DEBUG_ONLY)
 
 	if(NOT ANDROID AND _M_X86_64)
@@ -334,7 +338,6 @@ endif()
 
 
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
-	add_definitions(-D_DEBUG)
 
 	option(ENABLE_GPROF "Enable gprof profiling (must be using Debug build)" OFF)
 	if(ENABLE_GPROF)