cli: use Rust std library to get path to current exe — heartwood

This is more portable than reading /proc/self/exe, which only works on Linux.

Signed-off-by: Lars Wirzenius liw@liw.fi

     }));
     let debug = DebugInfo {
         rad_exe: if let Ok(filename) = std::fs::read_link("/proc/self/exe") {
         rad_exe: if let Ok(filename) = std::env::current_exe() {
             Some(filename)
         } else {
             None