test: bump cmake_minimum_required to 3.16

To address:

CMake Deprecation Warning at CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 3.5 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

Bump to a later version available in relatively recent Linux
distributions.

test/run.py

@@ -44,7 +44,7 @@ def test_cmake_build_system(build_dir, language, source, emulator, linker_flags,
     print('Building ' + source + ' with CMake...')
 
     with open('CMakeLists.txt', 'w') as fp:
-        fp.write('cmake_minimum_required(VERSION 3.0)\n')
+        fp.write('cmake_minimum_required(VERSION 3.16)\n')
         fp.write('project(test-compiler)\n')
         fp.write('add_executable(a.out ' + os.path.basename(source) + ')\n')
         if emulator: