File modern-cxx-standard.patch of Package libgav1

The example applications fail to build with such ancient C++ setting. Set the C++ standard instead to GCC's current version (17 as of GCC13)

--- a/CMakeLists.txt
+++ a/CMakeLists.txt
@@ -15,9 +15,6 @@
 # libgav1 requires modern CMake.
 cmake_minimum_required(VERSION 3.7.1 FATAL_ERROR)
 
-# libgav1 requires C++11.
-set(CMAKE_CXX_STANDARD 11)
-set(ABSL_CXX_STANDARD 11)
 # libgav1 requires C99.
 set(CMAKE_C_STANDARD 99)