Support old C++ compilers that don't have <filesystem>
Support old C++ compilers that don't have <filesystem>

Old C++ compilers such as g++ 7.x doesn't have <filesystem>, but
they sometimes have <experimental/filesystem> instead.

iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace