Improve default_target to respect current toolchain and config

Cargo.toml

@@ -14,7 +14,7 @@ edition = "2021"
 
 [dependencies]
 anyhow = "1.0.66"
-current_platform = "0.2.0"
+cargo-config2 = "0.1.19"
 clap = { version = "4.0.29", features = ["derive", "deprecated"] }
 tempfile = "3.3.0"
 toml = "0.5.9"

src/utils.rs

@@ -1,4 +1,20 @@
+use std::sync::OnceLock;
+
 /// The default target to pass to cargo, to workaround issue #11.
 pub fn default_target() -> &'static str {
-    current_platform::CURRENT_PLATFORM
+    // Use OnceLock because clap's default_value only accepts reference.
+    static DEFAULT_TARGET: OnceLock<String> = OnceLock::new();
+    DEFAULT_TARGET.get_or_init(|| {
+        let config = cargo_config2::Config::load().unwrap();
+        // Get the target specified in config.
+        let mut targets = config.build_target_for_cli(None::<&str>).unwrap();
+        if targets.len() > 1 {
+            // Config can contain multiple targets, but we don't support it: https://doc.rust-lang.org/cargo/reference/config.html#buildtarget
+            panic!("multi-target build is not supported: {targets:?}");
+        }
+        targets
+            .pop()
+            // Get the host triple if the target is not specified in config.
+            .unwrap_or_else(|| config.host_triple().unwrap().to_owned())
+    })
 }