build(engine): enforce C++17 in CMake and fix Data target standard

- Add CMAKE_CXX_STANDARD_REQUIRED ON and CMAKE_CXX_EXTENSIONS OFF
  to all three CMakeLists.txt files (Engine, gramambular2, Mandarin)
- Change Data target from gnu++0x (C++11) to c++17 in both Debug
  and Release configurations in project.pbxproj

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: tianjianjiang

McBopomofo.xcodeproj/project.pbxproj

@@ -1167,7 +1167,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
+				CLANG_CXX_LANGUAGE_STANDARD = "c++17";
 				CLANG_ENABLE_OBJC_WEAK = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COMBINE_HIDPI_IMAGES = YES;
@@ -1201,7 +1201,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
+				CLANG_CXX_LANGUAGE_STANDARD = "c++17";
 				CLANG_ENABLE_OBJC_WEAK = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COMBINE_HIDPI_IMAGES = YES;

Source/Engine/CMakeLists.txt

@@ -2,6 +2,8 @@ cmake_minimum_required(VERSION 3.6)
 project(McBopomofoLMLib)
 
 set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
 
 add_subdirectory(gramambular2)

Source/Engine/Mandarin/CMakeLists.txt

@@ -2,6 +2,8 @@ cmake_minimum_required(VERSION 3.6)
 project(Mandarin)
 
 set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
 
 add_library(MandarinLib Mandarin.h Mandarin.cpp)

Source/Engine/gramambular2/CMakeLists.txt

@@ -2,6 +2,8 @@ cmake_minimum_required(VERSION 3.6)
 project(gramambular2)
 
 set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
 
 add_library(gramambular2_lib language_model.h reading_grid.h reading_grid.cpp)