cmake: bump minimum version to address a deprecation warning

This fixes the following warning shown while configuring:

  [cmake] CMake Deprecation Warning at CMakeLists.txt:1 (cmake_minimum_required):
  [cmake] Compatibility with CMake < 3.10 will be removed from a future version of
  [cmake] CMake.

We don't have a clearly defined supported distro/versions list, so I
took Ubuntu 22.04 as arguably the oldest one we'd want to support for
the reference point. It has CMake 3.22, released in July 2022.

Signed-off-by: Alex T <alext.mkrs@gmail.com>

Author: alext-mkrs

CMakeLists.txt

@@ -1,15 +1,9 @@
-cmake_minimum_required (VERSION 2.8.11)
+cmake_minimum_required (VERSION 3.22)
 project (mraa C)
 
 FIND_PACKAGE (Threads REQUIRED)
 
-if (CMAKE_VERSION VERSION_LESS "3.1")
-  if (CMAKE_C_COMPILER_ID STREQUAL "GNU")
-    set (CMAKE_C_FLAGS "-std=gnu99 ${CMAKE_C_FLAGS}")
-  endif ()
-else ()
-  set (CMAKE_C_STANDARD 99)
-endif ()
+set (CMAKE_C_STANDARD 99)
 
 option (BUILDCPP "Enable C++ (needed by FTDI4222 and tests)" ON)