chore: generalize build.sh

build.rs

@@ -5,15 +5,17 @@ use std::{env, io::Error};
 include!("src/cli/mod.rs");
 
 fn main() -> Result<(), Error> {
-    let outdir = match env::var_os("OUT_DIR") {
-        None => return Ok(()),
-        Some(outdir) => outdir,
+    let outdir = env::var_os("SHELL_COMPLETIONS_DIR")
+        .or_else(|| env::var_os("OUT_DIR"));
+
+    let Some(outdir) = outdir else {
+        return Ok(());
     };
 
     let mut cmd = ahab::Ahab::command();
 
     for shell in Shell::value_variants() {
-        let path = generate_to(*shell, &mut cmd, "ahab", &outdir)?;
+        let path = generate_to(*shell, &mut cmd, env!("CARGO_PKG_NAME"), &outdir)?;
 
         println!("cargo:warning=completion file is generated: {path:?}");
     }