fixup: remove arm_llsc probe in build script

Cargo.toml

@@ -47,7 +47,7 @@ ufmt-write = { version = "0.1", optional = true }
 defmt = { version = ">=0.2.0,<0.4", optional = true }
 
 # for the pool module
-[target.'cfg(any(target_arch = "arm", target_arch = "aarch64", target_arch = "x86"))'.dependencies]
+[target.'cfg(any(target_arch = "arm", target_arch = "x86"))'.dependencies]
 stable_deref_trait = { version = "1", default-features = false }
 
 [dev-dependencies]

build.rs

@@ -26,67 +26,5 @@ fn main() -> Result<(), Box<dyn Error>> {
         _ => {}
     };
 
-    // AArch64 instruction set contains `clrex` but not `ldrex` or `strex`; the
-    // probe will succeed when we already know to deny this target from LLSC.
-    if !target.starts_with("aarch64") {
-        match compile_probe(ARM_LLSC_PROBE) {
-            Some(status) if status.success() => println!("cargo:rustc-cfg=arm_llsc"),
-            _ => {}
-        }
-    }
-
     Ok(())
 }
-
-const ARM_LLSC_PROBE: &str = r#"
-#![no_std]
-
-// `no_mangle` forces codegen, which makes llvm check the contents of the `asm!` macro
-#[no_mangle]
-unsafe fn asm() {
-    core::arch::asm!("clrex");
-}
-"#;
-
-// this function was taken from anyhow v1.0.63 build script
-// https://crates.io/crates/anyhow/1.0.63 (last visited 2022-09-02)
-// the code is licensed under 'MIT or APACHE-2.0'
-fn compile_probe(source: &str) -> Option<ExitStatus> {
-    let rustc = env::var_os("RUSTC")?;
-    let out_dir = env::var_os("OUT_DIR")?;
-    let probefile = Path::new(&out_dir).join("probe.rs");
-    fs::write(&probefile, source).ok()?;
-
-    // Make sure to pick up Cargo rustc configuration.
-    let mut cmd = if let Some(wrapper) = env::var_os("RUSTC_WRAPPER") {
-        let mut cmd = Command::new(wrapper);
-        // The wrapper's first argument is supposed to be the path to rustc.
-        cmd.arg(rustc);
-        cmd
-    } else {
-        Command::new(rustc)
-    };
-
-    cmd.stderr(Stdio::null())
-        .arg("--edition=2018")
-        .arg("--crate-name=probe")
-        .arg("--crate-type=lib")
-        .arg("--out-dir")
-        .arg(out_dir)
-        .arg(probefile);
-
-    if let Some(target) = env::var_os("TARGET") {
-        cmd.arg("--target").arg(target);
-    }
-
-    // If Cargo wants to set RUSTFLAGS, use that.
-    if let Ok(rustflags) = env::var("CARGO_ENCODED_RUSTFLAGS") {
-        if !rustflags.is_empty() {
-            for arg in rustflags.split('\x1f') {
-                cmd.arg(arg);
-            }
-        }
-    }
-
-    cmd.status().ok()
-}