Fix autodetect CMAKE_SYSTEM_VERSION to convert to Darwin version

conan/tools/cmake/toolchain/blocks.py

@@ -18,6 +18,7 @@
 from conan.tools.microsoft.visual import msvc_version_to_toolset_version
 from conans.client.subsystems import deduce_subsystem, WINDOWS
 from conan.errors import ConanException
+from conans.model.version import Version
 from conans.util.files import load
 
 
@@ -919,6 +920,33 @@ def _is_apple_cross_building(self):
         return os_host in ('iOS', 'watchOS', 'tvOS', 'visionOS') or (
                 os_host == 'Macos' and (arch_host != arch_build or os_build != os_host))
 
+    def _get_darwin_version(self, os_name, os_version):
+        version_mapping = {
+            "Macos": {
+                "10.13": "17", "10.14": "18", "10.15": "19", "11": "20",
+                "12": "21", "13": "22", "14": "23",
+            },
+            "iOS": {
+                "11": "17", "12": "18", "13": "19", "14": "20",
+                "15": "21", "16": "22", "17": "23"
+            },
+            "watchOS": {
+                "4": "17", "5": "18", "6": "19", "7": "20",
+                "8": "21", "9": "22", "10": "23"
+            },
+            "tvOS": {
+                "11": "17", "12": "18", "13": "19", "14": "20",
+                "15": "21", "16": "22", "17": "23"
+            },
+            "visionOS": {
+                "1": "23"
+            }
+        }
+        os_version = str(Version(os_version).major) \
+            if os_name != "Macos" or (os_name == "Macos" and Version(os_version) >= Version("11")) \
+            else str(os_version)
+        return version_mapping.get(os_name, {}).get(os_version)
+
     def _get_cross_build(self):
         user_toolchain = self._conanfile.conf.get("tools.cmake.cmaketoolchain:user_toolchain")
 
@@ -941,7 +969,8 @@ def _get_cross_build(self):
                     # cross-build in Macos also for M1
                     system_name = {'Macos': 'Darwin'}.get(os_host, os_host)
                     #  CMAKE_SYSTEM_VERSION for Apple sets the sdk version, not the os version
-                    _system_version = self._conanfile.settings.get_safe("os.sdk_version")
+                    sdk_version = self._conanfile.settings.get_safe("os.sdk_version")
+                    _system_version = self._get_darwin_version(os_host, sdk_version)
                     _system_processor = to_apple_arch(self._conanfile)
                 elif os_host != 'Android':
                     system_name = self._get_generic_system_name()

test/integration/toolchains/cmake/test_cmaketoolchain.py

@@ -85,7 +85,7 @@ def test_cross_build_linux_to_macos():
     toolchain = client.load("conan_toolchain.cmake")
 
     assert "set(CMAKE_SYSTEM_NAME Darwin)" in toolchain
-    assert "set(CMAKE_SYSTEM_VERSION 13.1)" in toolchain
+    assert "set(CMAKE_SYSTEM_VERSION 22)" in toolchain
     assert "set(CMAKE_SYSTEM_PROCESSOR x86_64)" in toolchain
 
 
@@ -437,7 +437,7 @@ def test_cmaketoolchain_cmake_system_processor_cross_apple():
     client.run("install hello.py -pr:h=./profile_ios -pr:b=default -g CMakeToolchain")
     toolchain = client.load("conan_toolchain.cmake")
     assert "set(CMAKE_SYSTEM_NAME iOS)" in toolchain
-    assert "set(CMAKE_SYSTEM_VERSION 15.0)" in toolchain
+    assert "set(CMAKE_SYSTEM_VERSION 21)" in toolchain
     assert "set(CMAKE_SYSTEM_PROCESSOR arm64)" in toolchain