Unrolled build for rust-lang#128636

Rollup merge of rust-lang#128636 - folkertdev:rmake-thumb-none-cortex-m, r=jieyouxu

migrate `thumb-none-cortex-m` to rmake

tracking issue: rust-lang#121876

I'll leave some comments/questions inline

r? ```@jieyouxu```

try-job: armhf-gnu
try-job: dist-various-1
try-job: test-various

src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -25,7 +25,6 @@ run-make/split-debuginfo/Makefile
 run-make/staticlib-dylib-linkage/Makefile
 run-make/symbol-mangling-hashed/Makefile
 run-make/sysroot-crates-are-unstable/Makefile
-run-make/thumb-none-cortex-m/Makefile
 run-make/thumb-none-qemu/Makefile
 run-make/translation/Makefile
 run-make/x86_64-fortanix-unknown-sgx-lvi/Makefile

tests/run-make/thumb-none-cortex-m/rmake.rs

@@ -0,0 +1,59 @@
+//! Test building of the `cortex-m` crate, a foundational crate in the embedded ecosystem
+//! for a collection of thumb targets. This is a smoke test that verifies that both cargo
+//! and rustc work in this case.
+//!
+//! How to run this
+//! $ ./x.py clean
+//! $ ./x.py test --target thumbv6m-none-eabi,thumbv7m-none-eabi tests/run-make
+//!
+//! Supported targets:
+//! - thumbv6m-none-eabi (Bare Cortex-M0, M0+, M1)
+//! - thumbv7em-none-eabi (Bare Cortex-M4, M7)
+//! - thumbv7em-none-eabihf (Bare Cortex-M4F, M7F, FPU, hardfloat)
+//! - thumbv7m-none-eabi (Bare Cortex-M3)
+
+//@ only-thumb
+
+use std::path::PathBuf;
+
+use run_make_support::rfs::create_dir;
+use run_make_support::{cmd, env_var, target};
+
+const CRATE: &str = "cortex-m";
+const CRATE_URL: &str = "https://github.com/rust-embedded/cortex-m";
+const CRATE_SHA1: &str = "a448e9156e2cb1e556e5441fd65426952ef4b927"; // v0.5.0
+
+fn main() {
+    // FIXME: requires an internet connection https://github.com/rust-lang/rust/issues/128733
+    // See below link for git usage:
+    // https://stackoverflow.com/questions/3489173#14091182
+    cmd("git").args(["clone", CRATE_URL, CRATE]).run();
+    std::env::set_current_dir(CRATE).unwrap();
+    cmd("git").args(["reset", "--hard", CRATE_SHA1]).run();
+
+    let target_dir = PathBuf::from("target");
+    let manifest_path = PathBuf::from("Cargo.toml");
+
+    let path = env_var("PATH");
+    let rustc = env_var("RUSTC");
+    let bootstrap_cargo = env_var("BOOTSTRAP_CARGO");
+    // FIXME: extract bootstrap cargo invocations to a proper command
+    // https://github.com/rust-lang/rust/issues/128734
+    let mut cmd = cmd(bootstrap_cargo);
+    cmd.args(&[
+        "build",
+        "--manifest-path",
+        manifest_path.to_str().unwrap(),
+        "-Zbuild-std=core",
+        "--target",
+        &target(),
+    ])
+    .env("PATH", path)
+    .env("RUSTC", rustc)
+    .env("CARGO_TARGET_DIR", &target_dir)
+    // Don't make lints fatal, but they need to at least warn
+    // or they break Cargo's target info parsing.
+    .env("RUSTFLAGS", "-Copt-level=0 -Cdebug-assertions=yes --cap-lints=warn");
+
+    cmd.run();
+}