rp: add precompiled boot2 to avoid depending on gcc

embassy-rp/build.rs

@@ -0,0 +1,17 @@
+use std::fs::{self, File};
+use std::io::Write;
+use std::path::{Path, PathBuf};
+use std::{env, ffi::OsStr};
+
+fn main() {
+    // Put the linker script somewhere the linker can find it
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    let link_x = include_bytes!("link-rp.x.in");
+    let mut f = File::create(out.join("link-rp.x")).unwrap();
+    f.write_all(link_x).unwrap();
+
+    println!("cargo:rustc-link-search={}", out.display());
+
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=link-rp.x.in");
+}

embassy-rp/link-rp.x.in

@@ -0,0 +1,8 @@
+
+SECTIONS {
+    /* ### Boot loader */
+    .boot2 ORIGIN(BOOT2) :
+    {
+        KEEP(*(.boot2));
+    } > BOOT2
+}

embassy-rp/src/system.rs

@@ -1,5 +1,9 @@
 use crate::{pac, pll, resets};
 
+#[link_section = ".boot2"]
+#[used]
+pub static BOOT2: [u8; 256] = *include_bytes!("boot2.bin");
+
 #[non_exhaustive]
 pub struct Config {}