Xcode: reject legacy buildsystem for Xcode 14

With Xcode 14 support for the Legacy Build System has been removed
and the BuildSystemType in the WorkspaceSettings is ignored.
If CMake still generates projects targeted to the Lecacy Build
System the build preparation phase will likely fail because Xcode
for example misses any declared outputs from script invocations.

This is a hard to debug problem and CMake should reject the invalid
configuration instead.

Help/release/dev/xcode-no-legacy-buildsystem.rst

@@ -0,0 +1,8 @@
+xcode-no-legacy-buildsystem
+---------------------------
+
+* The :generator:`Xcode` generator will now issue a fatal error if
+  the Legacy Build System has been selected for Xcode 14 and
+  newer. Those Xcode versions dropped support for the Legacy Build
+  System and expect the project being set-up for their current
+  Build System.

Help/variable/CMAKE_XCODE_BUILD_SYSTEM.rst

@@ -12,7 +12,8 @@ mature enough for use by CMake.  The possible values are:
 
 ``1``
   The original Xcode build system.
-  This is the default when using Xcode 11.x or below.
+  This is the default when using Xcode 11.x or below and supported
+  up to Xcode 13.x.
 
 ``12``
   The Xcode "new build system" introduced by Xcode 10.

Source/cmGlobalXCodeGenerator.cxx

@@ -407,8 +407,10 @@ bool cmGlobalXCodeGenerator::ProcessGeneratorToolsetField(
       mf->IssueMessage(MessageType::FATAL_ERROR, e);
       return false;
     }
-    if (this->XcodeBuildSystem == BuildSystem::Twelve &&
-        this->XcodeVersion < 120) {
+    if ((this->XcodeBuildSystem == BuildSystem::Twelve &&
+         this->XcodeVersion < 120) ||
+        (this->XcodeBuildSystem == BuildSystem::One &&
+         this->XcodeVersion >= 140)) {
       /* clang-format off */
       std::string const& e = cmStrCat(
         "Generator\n"

Tests/RunCMake/GeneratorToolset/BadToolsetXcodeBuildSystem1-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/GeneratorToolset/BadToolsetXcodeBuildSystem1-stderr.txt

@@ -0,0 +1,10 @@
+CMake Error at CMakeLists.txt:[0-9]+ \(project\):
+  Generator
+
+    Xcode
+
+  toolset specification field
+
+    buildsystem=1
+
+  is not allowed with Xcode [0-9.]+\.$

Tests/RunCMake/GeneratorToolset/BadToolsetXcodeBuildSystem1.cmake

@@ -0,0 +1 @@
+message(FATAL_ERROR "This should not be reached!")

Tests/RunCMake/GeneratorToolset/RunCMakeTest.cmake

@@ -89,7 +89,11 @@ elseif("${RunCMake_GENERATOR}" STREQUAL "Xcode")
     set(RunCMake_GENERATOR_TOOLSET "Test Toolset")
     run_cmake(TestToolsetXcodeBuildSystemDefault12)
     set(RunCMake_GENERATOR_TOOLSET "Test Toolset,buildsystem=1")
-    run_cmake(TestToolsetXcodeBuildSystem1)
+    if(XCODE_VERSION VERSION_GREATER_EQUAL 14)
+      run_cmake(BadToolsetXcodeBuildSystem1)
+    else()
+      run_cmake(TestToolsetXcodeBuildSystem1)
+    endif()
     set(RunCMake_GENERATOR_TOOLSET "Test Toolset,buildsystem=12")
     run_cmake(TestToolsetXcodeBuildSystem12)
   else()

Tests/RunCMake/XcodeProject-Device/RunCMakeTest.cmake

@@ -311,9 +311,11 @@ if (XCODE_VERSION VERSION_GREATER_EQUAL 7.3)
   endfunction()
 
   if(XCODE_VERSION VERSION_GREATER_EQUAL 12)
-    xctest_add_bundle_test(Darwin macosx "1" "$<TARGET_BUNDLE_CONTENT_DIR:TestedApp>/PlugIns")
     xctest_add_bundle_test(Darwin macosx "12" "$<TARGET_BUNDLE_CONTENT_DIR:TestedApp>/PlugIns")
-    xctest_add_bundle_test(iOS iphonesimulator "1" "$<TARGET_BUNDLE_CONTENT_DIR:TestedApp>/PlugIns")
+    if(XCODE_VERSION VERSION_LESS 14)
+      xctest_add_bundle_test(Darwin macosx "1" "$<TARGET_BUNDLE_CONTENT_DIR:TestedApp>/PlugIns")
+      xctest_add_bundle_test(iOS iphonesimulator "1" "$<TARGET_BUNDLE_CONTENT_DIR:TestedApp>/PlugIns")
+    endif()
     if (XCODE_VERSION VERSION_LESS 12.5)
       xctest_add_bundle_test(iOS iphonesimulator "12" "$<TARGET_BUNDLE_CONTENT_DIR:TestedApp>")
     else()