Fix build of the rpi baremetal target (#150)

The problem was this bug in rust/llvm - rust-lang/rust#127269

- Fix the git version not updating when the common is not rebuilt by setting it to rebuild upon git head changing.
- Delete .cargo/config.toml and replace it with build script to make it simpler
- Move the config.txt output to the artifacts folder

Makefile.toml

@@ -45,7 +45,6 @@ dependencies = ["build_rpi_baremetal","install_llvm_tools"]
 
 [tasks.build_rpi_baremetal]
 toolchain = "nightly"
-cwd = "./rpi/"
 command = "cargo"
 args = ["build", "--release", "--target", "armv7a-none-eabihf","--package", "magenboy_rpi", "--bin", "baremetal", "-Z", "build-std=core"]
 dependencies = ["install_rust_src"]

common/build.rs

@@ -1,6 +1,13 @@
 use std::process::Command;
 
 fn main() {
+    let git_path = std::path::Path::new("../.git");
+    let head_path = git_path.join("HEAD");
+    let current_branch = std::fs::read_to_string(&head_path).unwrap().replace("refs: ", "");
+    let current_commit_file = git_path.join(&current_branch);
+    println!("cargo:rerun-if-changed={}", head_path.to_str().unwrap());
+    println!("cargo:rerun-if-changed={}", current_commit_file.to_str().unwrap());
+
     let output = Command::new("git").args(&["rev-parse", "--short", "HEAD"]).output().unwrap();
     let git_hash = String::from_utf8(output.stdout).unwrap();
     let version = env!("CARGO_PKG_VERSION");

rpi/build.rs

@@ -2,7 +2,6 @@
 mod config{
     pub const RPI_ENV_VAR_NAME:&'static str = "RPI";
     pub const LD_SCRIPT_PATH:&str = "src/bin/baremetal/link.ld";
-    pub const CONFIG_FILE_PATH: &str = "config.txt";
     pub const CONFIG_TXT_CONTENT:&str = 
 "# configuration for the RPI
 arm_64bit=0 # boot to 32 bit mode
@@ -21,14 +20,33 @@ fn main(){
     }
     #[cfg(not(feature = "os"))]
     {
-        println!("cargo:rerun-if-changed={}", config::LD_SCRIPT_PATH);
+        let crate_manifest_path = env!("CARGO_MANIFEST_DIR");
+        let ld_script_path = std::path::Path::new(crate_manifest_path).join(config::LD_SCRIPT_PATH);
+        let ld_script_path = ld_script_path.to_str().unwrap();
+
+        println!("cargo:rerun-if-changed={}", ld_script_path);
         println!("cargo:rerun-if-env-changed={}", config::RPI_ENV_VAR_NAME);
 
+        // Linker script
+        println!("cargo:rustc-link-arg-bin=baremetal={}", ld_script_path);
+
         // Creates config.txt
-        std::fs::write(config::CONFIG_FILE_PATH, config::CONFIG_TXT_CONTENT).unwrap();
+        let out_dir = std::env::var("OUT_DIR").unwrap();
+        // Turns the out dir to the artifacts dir
+        let mut config_file_path = std::path::Path::new(&out_dir).to_path_buf();
+        config_file_path.pop();
+        config_file_path.pop();
+        config_file_path.pop();
+        config_file_path = config_file_path.join("config.txt");
+        std::fs::write(config_file_path, config::CONFIG_TXT_CONTENT).unwrap();
 
         // Add the cfg option `rpi` with that value of the env var `RPI`
-        let rpi_revision = std::env::var(config::RPI_ENV_VAR_NAME).expect("RPI env must be set");
-        println!("cargo:rustc-cfg=rpi=\"{}\"", rpi_revision);
+        let rpi_version = std::env::var(config::RPI_ENV_VAR_NAME)
+            .expect(std::format!("{} env must be set", config::RPI_ENV_VAR_NAME).as_str());
+        println!("cargo:rustc-cfg=rpi=\"{}\"", rpi_version);
+
+        // Silent warnings for this cfg 
+        println!("cargo::rustc-check-cfg=cfg(rpi, values(\"4\", \"2\"))");
+        println!("cargo::rustc-check-cfg=cfg(rpi)");
     }
 }

rpi/src/bin/baremetal/boot_armv7a.s

@@ -1,3 +1,7 @@
+// Enabling all the features of the cortex-a72, currently rust has a bug preventing enabling with rustc 
+// For more see - https://github.com/rust-lang/rust/issues/127269
+.cpu cortex-a72
+
 // alias the PERIPHERALS_BASE_ADDRESS symbol at pointer
 // since it is a static global variable from the rust side
 .equ    PERIPHERALS_BASE_ADDRESS_PTR,   PERIPHERALS_BASE_ADDRESS