build: add shared guest program build

tools/risc0-packager/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "risc0-packager"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+anyhow = "1"
+risc0-binfmt = "=3.0.4"
+risc0-build = "=3.0.5"
+
+[lints]
+workspace = true

tools/risc0-packager/src/main.rs

@@ -0,0 +1,52 @@
+use std::{env, ffi::OsString, fs, path::PathBuf};
+
+use anyhow::{bail, Context, Result};
+use risc0_binfmt::ProgramBinary;
+
+fn main() -> Result<()> {
+    let mut args = env::args_os();
+    let command = args
+        .next()
+        .unwrap_or_else(|| OsString::from("risc0-packager"));
+    let input = required_arg(&mut args, &command, "guest ELF")?;
+    let output = required_arg(&mut args, &command, "output .bin")?;
+
+    if args.next().is_some() {
+        bail!(
+            "usage: {} <guest-elf> <output-bin>",
+            command.to_string_lossy()
+        );
+    }
+
+    if let Some(parent) = output
+        .parent()
+        .filter(|parent| !parent.as_os_str().is_empty())
+    {
+        fs::create_dir_all(parent)
+            .with_context(|| format!("failed to create {}", parent.display()))?;
+    }
+
+    let user_elf =
+        fs::read(&input).with_context(|| format!("failed to read {}", input.display()))?;
+    let kernel_elf = risc0_build::GuestOptions::default().kernel();
+    let binary = ProgramBinary::new(&user_elf, &kernel_elf);
+
+    fs::write(&output, binary.encode())
+        .with_context(|| format!("failed to write {}", output.display()))?;
+
+    Ok(())
+}
+
+fn required_arg(
+    args: &mut impl Iterator<Item = OsString>,
+    command: &OsString,
+    name: &str,
+) -> Result<PathBuf> {
+    match args.next() {
+        Some(value) => Ok(PathBuf::from(value)),
+        None => bail!(
+            "missing {name}; usage: {} <guest-elf> <output-bin>",
+            command.to_string_lossy()
+        ),
+    }
+}