Allow setting entrypoint from CLI

src/cli.rs

@@ -62,6 +62,10 @@ pub struct Args {
     #[arg(long = "bwrap-arg", value_name = "ARG", action = clap::ArgAction::Append)]
     pub bwrap_args: Vec<String>,
 
+    /// Run this binary with the trailing args as its arguments
+    #[arg(long, value_name = "CMD")]
+    pub entrypoint: Option<String>,
+
     /// Command and arguments to run inside the sandbox
     #[arg(trailing_var_arg = true, allow_hyphen_values = true)]
     pub command_and_args: Vec<OsString>,