#3392 (part of zstd 1.5.4) checks linker flags in CMake build by relying on https://cmake.org/cmake/help/latest/module/CheckLinkerFlag.html, a function available since CMake 3.18. But cmake_minimum_required() of main CMakeLists is still 2.8.12.
Is it intentional to use such recent feature? If it is, cmake_minimum_required() should be updated accordingly. Otherwise it's possible to achieve the same checks by using check_source_compiles() and therefore avoid constraining CMakeLists of zstd to such recent CMake version.