veristat: @files-list.txt notation for object files list

veristat: @files-list.txt notation for object files list

Allow reading object file list from file.
E.g. the following command:

  ./veristat @list.txt

Is equivalent to the following invocation:

  ./veristat line-1 line-2 ... line-N

Where line-i corresponds to lines from list.txt.
Lines starting with '#' are ignored.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>
Link: https://lore.kernel.org/bpf/20250301000147.1583999-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>