Remove the need for a linker script and move multiboot to a feature

agb/Cargo.toml

@@ -10,6 +10,7 @@ repository = "https://github.com/agbrs/agb"
 [features]
 default = ["testing"]
 testing = []
+multiboot = []
 
 [dependencies]
 bitflags = "2"

agb/build.rs

@@ -1,5 +1,19 @@
-fn main() {
+use std::{env, error::Error, fs, path::PathBuf};
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let out = &PathBuf::from(env::var("OUT_DIR").unwrap());
+    let linker_script = if env::var("CARGO_FEATURE_MULTIBOOT").is_ok() {
+        include_bytes!("gba_mb.ld").as_slice()
+    } else {
+        include_bytes!("gba.ld").as_slice()
+    };
+
+    fs::write(out.join("gba.ld"), linker_script)?;
+    println!("cargo:rustc-link-search={}", out.display());
+
     println!("cargo:rerun-if-changed=gba.ld");
     println!("cargo:rerun-if-changed=gba_mb.ld");
     println!("cargo:rerun-if-changed=build.rs");
+
+    Ok(())
 }