add build.rs script to set linker flags

.cargo/config.toml

@@ -2,9 +2,5 @@
 runner = "probe-run --chip stm32g031j6mx"
 # runner = 'arm-none-eabi-size -G'
 
-rustflags = [
-  "-C", "link-arg=-Tlink.x",
-]
-
 [build]
 target = "thumbv6m-none-eabi"

build.rs

@@ -0,0 +1,43 @@
+//! This build script copies the `memory.x` file from the crate root into
+//! a directory where the linker can always find it at build time.
+//! For many projects this is optional, as the linker always searches the
+//! project root directory -- wherever `Cargo.toml` is. However, if you
+//! are using a workspace or have a more complicated build setup, this
+//! build script becomes required. Additionally, by requesting that
+//! Cargo re-run the build script whenever `memory.x` is changed,
+//! updating `memory.x` ensures a rebuild of the application with the
+//! new memory settings.
+//!
+//! The build script also sets the linker flags to tell it which link script to use.
+
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
+fn main() {
+    // Put `memory.x` in our output directory and ensure it's
+    // on the linker search path.
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    File::create(out.join("memory.x"))
+        .unwrap()
+        .write_all(include_bytes!("memory.x"))
+        .unwrap();
+    println!("cargo:rustc-link-search={}", out.display());
+
+    // By default, Cargo will re-run a build script whenever
+    // any file in the project changes. By specifying `memory.x`
+    // here, we ensure the build script is only re-run when
+    // `memory.x` is changed.
+    println!("cargo:rerun-if-changed=memory.x");
+
+    // Specify linker arguments.
+
+    // `--nmagic` is required if memory section addresses are not aligned to 0x10000,
+    // for example the FLASH and RAM sections in your `memory.x`.
+    // See https://github.com/rust-embedded/cortex-m-quickstart/pull/95
+    println!("cargo:rustc-link-arg=--nmagic");
+
+    // Set the linker script to the one provided by cortex-m-rt.
+    println!("cargo:rustc-link-arg=-Tlink.x");
+}