depends: switch to building expat with CMake

Add a patch to set the minimum CMake to 3.16.

depends/patches/expat/cmake_minimum.patch

@@ -0,0 +1,13 @@
+build: set minimum required CMake to 3.16
+
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -33,7 +33,7 @@
+ # Unlike most of Expat,
+ # this file is copyrighted under the BSD-license for buildsystem files of KDE.
+ 
+-cmake_minimum_required(VERSION 3.1.3)
++cmake_minimum_required(VERSION 3.16)
+ 
+ # This allows controlling documented build time switches
+ # when Expat is pulled in using the add_subdirectory function, e.g.