feat: rerun build if linker script changes

Makefile

@@ -66,7 +66,7 @@ endif
 all: kernel initrd
 
 kernel:
-	cd kernel && cargo build $(CARGO_BUILD_OPTS)
+	cd kernel && ARCH=$(ARCH) MACH=$(MACH) cargo build $(CARGO_BUILD_OPTS)
 ifeq ($(ARCH),aarch64)
 	$(LLVM_BASE)/llvm-strip -o $(O)/kernel.strip $(O)/kernel
 	$(LLVM_BASE)/llvm-size $(O)/kernel.strip

kernel/build.rs

@@ -0,0 +1,12 @@
+use std::env;
+
+fn main() -> Result<(), i32> {
+    let arch = env::var("ARCH").expect("$ARCH is not set");
+    let mach = if arch == "aarch64" {
+        env::var("MACH").expect("$MACH is not set")
+    } else {
+        "none".to_owned()
+    };
+    println!("cargo:rerun-if-changed=../etc/{}-{}.ld", arch, mach);
+    Ok(())
+}