Add target setting that enables building one architecture only

Fixes #62

src/commands/package.rs

@@ -58,6 +58,7 @@ pub struct FeatureOptions {
 #[allow(clippy::too_many_arguments)]
 pub fn run(
     platforms: Option<Vec<Platform>>,
+    build_target: Option<&str>,
     package_name: Option<String>,
     xcframework_name: String,
     disable_warnings: bool,
@@ -77,6 +78,7 @@ pub fn run(
         return run_for_crate(
             crates[0],
             platforms.clone(),
+            build_target,
             package_name,
             xcframework_name,
             disable_warnings,
@@ -97,6 +99,7 @@ pub fn run(
             run_for_crate(
                 current_crate,
                 platforms.clone(),
+                build_target,
                 None,
                 xcframework_name.clone(),
                 disable_warnings,
@@ -116,6 +119,7 @@ pub fn run(
 fn run_for_crate(
     current_crate: &Package,
     platforms: Option<Vec<Platform>>,
+    build_target: Option<&str>,
     package_name: Option<String>,
     xcframework_name: String,
     disable_warnings: bool,
@@ -154,12 +158,40 @@ fn run_for_crate(
         Err("At least 1 platform needs to be selected!")?;
     }
 
-    let targets: Vec<_> = platforms
+    let mut targets: Vec<_> = platforms
         .into_iter()
         .flat_map(|p| p.into_apple_platforms())
         .map(|p| p.target())
         .collect();
 
+    if let Some(build_target) = build_target {
+        targets.retain_mut(|platform_target| match platform_target {
+            Target::Single { architecture, .. } => *architecture == build_target,
+            Target::Universal {
+                architectures,
+                display_name,
+                platform,
+                ..
+            } => {
+                let Some(architecture) = architectures.iter().find(|t| **t == build_target) else {
+                    return false;
+                };
+                *platform_target = Target::Single {
+                    architecture,
+                    display_name,
+                    platform: *platform,
+                };
+                true
+            }
+        });
+        if targets.is_empty() {
+            return Err(Error::from(format!(
+                "No matching build target for {}",
+                build_target
+            )));
+        }
+    }
+
     if !skip_toolchains_check {
         let missing_toolchains = check_installed_toolchains(&targets);
         let nightly_toolchains = check_nightly_installed(&targets);

src/main.rs

@@ -74,6 +74,10 @@ enum Action {
         #[arg(short, long, trailing_var_arg = true, num_args = 1..=4, ignore_case = true)]
         platforms: Option<Vec<package::Platform>>,
 
+        #[arg(long)]
+        /// Build package for the specified target triplet only.
+        target: Option<String>,
+
         #[arg(short = 'n', long = "name")]
         package_name: Option<String>,
 
@@ -122,6 +126,7 @@ fn main() -> ExitCode {
 
         Action::Package {
             platforms,
+            target,
             package_name,
             xcframework_name,
             suppress_warnings,
@@ -133,6 +138,7 @@ fn main() -> ExitCode {
             no_default_features,
         } => package::run(
             platforms,
+            target.as_deref(),
             package_name,
             xcframework_name,
             suppress_warnings,

src/targets.rs

@@ -51,7 +51,11 @@ impl Target {
             .into_iter()
             .map(|arch| {
                 // FIXME: Remove nightly for Tier 3 targets here once build-std is stabilized
-                let mut cmd = if self.platform().is_tier_3() { command("cargo +nightly build -Z build-std") } else { command("cargo build") };
+                let mut cmd = if self.platform().is_tier_3() {
+                    command("cargo +nightly build -Z build-std")
+                } else {
+                    command("cargo build")
+                };
                 cmd.arg("--target").arg(arch);
 
                 match mode {