add an option to pass an arbitrary set of arguments to cargo build

src/build.rs

@@ -68,6 +68,7 @@ pub fn cargo_build_wasm(
     path: &Path,
     profile: BuildProfile,
     step: &Step,
+    extra_options: &Vec<String>,
 ) -> Result<(), Error> {
     let msg = format!("{}Compiling to WASM...", emoji::CYCLONE);
     PBAR.step(step, &msg);
@@ -91,6 +92,7 @@ pub fn cargo_build_wasm(
         }
     }
     cmd.arg("--target").arg("wasm32-unknown-unknown");
+    cmd.args(extra_options);
     child::run(log, cmd, "cargo build").context("Compiling your crate to WebAssembly failed")?;
     Ok(())
 }

src/command/build.rs

@@ -30,6 +30,7 @@ pub struct Build {
     pub out_dir: PathBuf,
     pub bindgen: Option<Download>,
     pub cache: Cache,
+    pub extra_options: Vec<String>,
 }
 
 /// The `BuildMode` determines which mode of initialization we are running, and
@@ -119,6 +120,10 @@ pub struct BuildOptions {
     #[structopt(long = "out-dir", short = "d", default_value = "pkg")]
     /// Sets the output directory with a relative path.
     pub out_dir: String,
+
+    #[structopt(last = true)]
+    /// List of extra options to pass to `cargo build`
+    extra_options: Vec<String>,
 }
 
 type BuildStep = fn(&mut Build, &Step, &Logger) -> Result<(), Error>;
@@ -151,6 +156,7 @@ impl Build {
             out_dir,
             bindgen: None,
             cache: Cache::new()?,
+            extra_options: build_opts.extra_options,
         })
     }
 
@@ -255,7 +261,13 @@ impl Build {
 
     fn step_build_wasm(&mut self, step: &Step, log: &Logger) -> Result<(), Error> {
         info!(&log, "Building wasm...");
-        build::cargo_build_wasm(log, &self.crate_path, self.profile, step)?;
+        build::cargo_build_wasm(
+            log, 
+            &self.crate_path, 
+            self.profile, 
+            step, 
+            &self.extra_options,
+        )?;
 
         info!(
             &log,