Merge commit '3a31c6d827' into sync_cg_clif-2021-07-07

compiler/rustc_codegen_cranelift/build_system/build_backend.rs

@@ -0,0 +1,40 @@
+use std::env;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+pub(crate) fn build_backend(channel: &str, host_triple: &str) -> PathBuf {
+    let mut cmd = Command::new("cargo");
+    cmd.arg("build").arg("--target").arg(host_triple);
+
+    match channel {
+        "debug" => {}
+        "release" => {
+            cmd.arg("--release");
+        }
+        _ => unreachable!(),
+    }
+
+    if cfg!(unix) {
+        if cfg!(target_os = "macos") {
+            cmd.env(
+                "RUSTFLAGS",
+                "-Csplit-debuginfo=unpacked \
+                -Clink-arg=-Wl,-rpath,@loader_path/../lib \
+                -Zosx-rpath-install-name"
+                    .to_string()
+                    + env::var("RUSTFLAGS").as_deref().unwrap_or(""),
+            );
+        } else {
+            cmd.env(
+                "RUSTFLAGS",
+                "-Clink-arg=-Wl,-rpath=$ORIGIN/../lib ".to_string()
+                    + env::var("RUSTFLAGS").as_deref().unwrap_or(""),
+            );
+        }
+    }
+
+    eprintln!("[BUILD] rustc_codegen_cranelift");
+    crate::utils::spawn_and_wait(cmd);
+
+    Path::new("target").join(host_triple).join(channel)
+}