feat(OS): Create basic kernel that can be run through both QEMU and on hardware (#1)

Reviewed-on: #1

build.rs

@@ -0,0 +1,21 @@
+use std::path::PathBuf;
+
+fn main() {
+    // set by cargo, build scripts should use this directory for output files
+    let out_dir = PathBuf::from(std::env::var_os("OUT_DIR").unwrap());
+    // set by cargo's artifact dependency feature, see
+    // https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#artifact-dependencies
+    let kernel = PathBuf::from(std::env::var_os("CARGO_BIN_FILE_KERNEL_kernel").unwrap());
+
+    // create an UEFI disk image (optional)
+    let uefi_path = out_dir.join("uefi.img");
+    bootloader::UefiBoot::new(&kernel).create_disk_image(&uefi_path).unwrap();
+
+    // create a BIOS disk image
+    let bios_path = out_dir.join("bios.img");
+    bootloader::BiosBoot::new(&kernel).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());
+    println!("cargo:rustc-env=BIOS_PATH={}", bios_path.display());
+}