Fix Create Disk Image Example

The example code didn't compile. This patch fixes that.

Author: AlexJMohr

docs/create-disk-image.md

@@ -38,20 +38,28 @@ members = ["kernel"]
 ```rust
 // build.rs
 
+use std::path::Path;
+
 fn main() {
     // set by cargo, build scripts should use this directory for output files
     let out_dir = std::env::var_os("OUT_DIR").unwrap();
+    let out_dir_path = Path::new(&out_dir);
     // set by cargo's artifact dependency feature, see
     // https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#artifact-dependencies
-    let kernel = std::env::var_os("CARGO_BIN_FILE_KERNEL_kernel");
+    let kernel = std::env::var_os("CARGO_BIN_FILE_KERNEL_kernel").unwrap();
+    let kernel_path = Path::new(&kernel);
 
     // create an UEFI disk image (optional)
-    let uefi_path = out_dir.join("uefi.img");
-    bootloader::UefiBoot::new(&kernel).create_disk_image(uefi_path).unwrap();
+    let uefi_path = out_dir_path.join("uefi.img");
+    bootloader::UefiBoot::new(&kernel_path)
+        .create_disk_image(&uefi_path)
+        .unwrap();
 
-    // create a BIOS disk image (optional)
-    let out_bios_path = out_dir.join("bios.img");
-    bootloader::BiosBoot::new(&kernel).create_disk_image(uefi_path).unwrap();
+    // create a BIOS disk image
+    let bios_path = out_dir_path.join("bios.img");
+    bootloader::BiosBoot::new(&kernel_path)
+        .create_disk_image(&bios_path)
+        .unwrap();
 
     // pass the disk image paths as env variables to the `main.rs`
     println!("cargo:rustc-env=UEFI_PATH={}", uefi_path.display());
@@ -77,8 +85,8 @@ fn main() {
     } else {
         cmd.arg("-drive").arg(format!("format=raw,file={bios_path}"));
     }
-    let mut child = cmd.spawn()?;
-    child.wait()?;
+    let mut child = cmd.spawn().unwrap();
+    child.wait().unwrap();
 }
 ```