OSX detect_api.sdk_version (#16355)

* OSX detect_api.sdk_version

* add Darwin check

* fix

conan/internal/api/detect_api.py

@@ -581,3 +581,12 @@ def default_compiler_version(compiler, version):
     elif compiler == "intel-cc":
         return major
     return version
+
+
+def detect_sdk_version(sdk):
+    if platform.system() != "Darwin":
+        return
+    cmd = f'xcrun -sdk {sdk} --show-sdk-version'
+    result = check_output_runner(cmd)
+    result = result.strip()
+    return result

test/functional/test_profile_detect_api.py

@@ -76,3 +76,17 @@ def test_profile_detect_libc(self):
             user.confvar:libc_version={libc_version}
             """)
         assert expected in client.out
+
+    @pytest.mark.skipif(platform.system() != "Darwin", reason="Only OSX")
+    def test_profile_detect_darwin_sdk(self):
+        client = TestClient()
+        tpl1 = textwrap.dedent("""\
+            [settings]
+            os = "Macos"
+            os.sdk_version = {{ detect_api.detect_sdk_version(sdk="macosx")  }}
+            """)
+
+        client.save({"profile1": tpl1})
+        client.run("profile show -pr=profile1")
+        sdk_version = detect_api.detect_sdk_version(sdk="macosx")
+        assert f"os.sdk_version={sdk_version}" in client.out