Update xcodetoolchain.rst (#4126)

Author: kambala-decapitator

reference/tools/apple/xcodetoolchain.rst

@@ -63,8 +63,8 @@ Those files are:
   files from this generator and the generated by the
   :ref:`XcodeDeps<conan_tools_apple_xcodedeps>` in case it was also set.
 - *conantoolchain_<debug/release>_x86_64.xcconfig*: declares ``CLANG_CXX_LIBRARY``,
-  ``CLANG_CXX_LANGUAGE_STANDARD`` and ``MACOSX_DEPLOYMENT_TARGET`` variables with
-  conditional logic depending on the build configuration, architecture and sdk set.
+  ``CLANG_CXX_LANGUAGE_STANDARD`` and ``MACOSX_DEPLOYMENT_TARGET`` (when ``os`` is set to ``Macos``)
+  variables with conditional logic depending on the build configuration, architecture and sdk set.
 - *conantoolchain.xcconfig*: aggregates all the *conantoolchain_<config>_<arch>.xcconfig*
   files for the different installed configurations.
 - *conan_global_flags.xcconfig*: this file will only be generated in case of any
@@ -79,9 +79,10 @@ project.
 
 The XcodeToolchain files can declare the following Xcode build settings based on Conan settings values:
 
-- ``MACOSX_DEPLOYMENT_TARGET`` is based on the value of the ``os.version`` setting and
-  will make the build system to pass the flag ``-mmacosx-version-min`` with that value (if
-  set). It defines the operating system version the binary should run into.
+- ``*_DEPLOYMENT_TARGET`` is based on the value of the ``os`` + ``os.version`` settings and
+  will make the build system pass respective flag (e.g. ``MACOSX_DEPLOYMENT_TARGET`` translates to
+  ``-mmacosx-version-min`` for macOS) with that value (if set). It defines the minimum operating
+  system version the binary should run on.
 - ``CLANG_CXX_LANGUAGE_STANDARD`` is based on the value of the ``compiler.cppstd`` setting
   that sets the C++ language standard.
 - ``CLANG_CXX_LIBRARY`` is based on the value of the compiler.libcxx setting and sets the