Better handling when host target == cross compile target

src/cli.rs

@@ -1,8 +1,9 @@
 use std::env;
 use std::path::PathBuf;
 use std::process::{self, Command};
+use std::str;
 
-use anyhow::{Context, Result};
+use anyhow::{bail, format_err, Context, Result};
 use clap::Parser;
 use fs_err as fs;
 
@@ -292,17 +293,21 @@ impl Build {
 
         // setup zig as linker
         if let Some(target) = self.target.as_ref() {
-            if let Some(rust_target) = rust_target {
-                let (zig_cc, zig_cxx) = prepare_zig_linker(target)?;
-                let env_target = rust_target.to_uppercase().replace("-", "_");
-                build.env("TARGET_CC", &zig_cc);
-                build.env("TARGET_CXX", &zig_cxx);
-                build.env(format!("CARGO_TARGET_{}_LINKER", env_target), &zig_cc);
-
-                self.setup_os_deps()?;
-
-                if rust_target.contains("windows-gnu") {
-                    build.env("WINAPI_NO_BUNDLED_LIBRARIES", "1");
+            let host_target = get_host_target()?;
+            // we only setup zig as linker when target isn't exactly the same as host target
+            if host_target != *target {
+                if let Some(rust_target) = rust_target {
+                    let (zig_cc, zig_cxx) = prepare_zig_linker(target)?;
+                    let env_target = rust_target.to_uppercase().replace("-", "_");
+                    build.env("TARGET_CC", &zig_cc);
+                    build.env("TARGET_CXX", &zig_cxx);
+                    build.env(format!("CARGO_TARGET_{}_LINKER", env_target), &zig_cc);
+
+                    self.setup_os_deps()?;
+
+                    if rust_target.contains("windows-gnu") {
+                        build.env("WINAPI_NO_BUNDLED_LIBRARIES", "1");
+                    }
                 }
             }
         }
@@ -355,3 +360,37 @@ impl Build {
         Ok(())
     }
 }
+
+fn get_host_target() -> Result<String> {
+    let output = Command::new("rustc").arg("-vV").output();
+    let output = match output {
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
+            bail!(
+                "rustc, the rust compiler, is not installed or not in PATH. \
+                This package requires Rust and Cargo to compile extensions. \
+                Install it through the system's package manager or via https://rustup.rs/.",
+            );
+        }
+        Err(err) => {
+            return Err(err).context("Failed to run rustc to get the host target");
+        }
+        Ok(output) => output,
+    };
+
+    let output = str::from_utf8(&output.stdout).context("`rustc -vV` didn't return utf8 output")?;
+
+    let field = "host: ";
+    let host = output
+        .lines()
+        .find(|l| l.starts_with(field))
+        .map(|l| &l[field.len()..])
+        .ok_or_else(|| {
+            format_err!(
+                "`rustc -vV` didn't have a line for `{}`, got:\n{}",
+                field.trim(),
+                output
+            )
+        })?
+        .to_string();
+    Ok(host)
+}