cmake: set minimum required version to 3.10

[fanquake]

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

  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.
This warning is for project developers.  Use -Wno-author or -Wno-deprecated
to suppress it.