Try using cmake_parse_arguments to make the macro work

cmake/OpenMWMacros.cmake

@@ -143,8 +143,34 @@ add_hdr (OPENCS ${dir} ${u})
 endforeach (u)
 endmacro (opencs_hdrs_noqt)
 
+include(CMakeParseArguments)
+
 macro (openmw_add_executable target)
-	add_executable(${target} ${ARGN})
+	set(OMW_ADD_EXE_OPTIONS WIN32 MACOSX_BUNDLE EXCLUDE_FROM_ALL)
+	set(OMW_ADD_EXE_VALUES)
+	set(OMW_ADD_EXE_MULTI_VALUES)
+	cmake_parse_arguments(OMW_ADD_EXE "${OMW_ADD_EXE_OPTIONS}" "${OMW_ADD_EXE_VALUES}" "${OMW_ADD_EXE_MULTI_VALUES}" ${ARGN})
+	
+	if (OMW_ADD_EXE_WIN32)
+		set(OMW_ADD_EXE_WIN32_VALUE WIN32)
+	endif (OMW_ADD_EXE_WIN32)
+	
+	if (OMW_ADD_EXE_MACOSX_BUNDLE)
+		set(OMW_ADD_EXE_MACOSX_BUNDLE_VALUE MACOSX_BUNDLE)
+	endif (OMW_ADD_EXE_MACOSX_BUNDLE)
+	
+	if (OMW_ADD_EXE_EXCLUDE_FROM_ALL)
+		set(OMW_ADD_EXE_EXCLUDE_FROM_ALL_VALUE EXCLUDE_FROM_ALL)
+	endif (OMW_ADD_EXE_EXCLUDE_FROM_ALL)
+	
+	message("Target: " ${target})
+	message("WIN32: ${OMW_ADD_EXE_WIN32_VALUE}")
+	message("MACOSX_BUNDLE: ${OMW_ADD_EXE_MACOSX_BUNDLE_VALUE}")
+	message("EXCLUDE_FROM_ALL: ${OMW_ADD_EXE_EXCLUDE_FROM_ALL_VALUE}")
+	message("Unparsed: ${OMW_ADD_EXE_UNPARSED_ARGUMENTS}")
+	
+	add_executable(${target} ${OMW_ADD_EXE_WIN32_VALUE} ${OMW_ADD_EXE_MACOSX_BUNDLE_VALUE} ${OMW_ADD_EXE_EXCLUDE_FROM_ALL_VALUE} "${OMW_ADD_EXE_UNPARSED_ARGUMENTS}")
+	
 	if (MSVC)
 		if (CMAKE_VERSION VERSION_GREATER 3.8 OR CMAKE_VERSION VERSION_EQUAL 3.8)
 			set_target_properties(${target} PROPERTIES VS_DEBUGGER_WORKING_DIRECTORY "$(TargetDir)")