Simplify some code in ndk-macro and ndk-build (#162)

* ndk-macro/helper: Use `as_deref()` instead of temporary in `map()`

* ndk-build: Deduplicate library path formatting in UnalignedApk::add_lib

ndk-build/src/apk.rs

@@ -79,17 +79,13 @@ impl<'a> UnalignedApk<'a> {
             return Err(NdkError::PathNotFound(path.into()));
         }
         let abi = target.android_abi();
-        let file_name = path.file_name().unwrap();
-        let out = self.0.build_dir.join("lib").join(abi);
-        std::fs::create_dir_all(&out)?;
-        std::fs::copy(path, out.join(&file_name))?;
+        let lib_path = Path::new("lib").join(abi).join(path.file_name().unwrap());
+        let out = self.0.build_dir.join(&lib_path);
+        std::fs::create_dir_all(out.parent().unwrap())?;
+        std::fs::copy(path, out)?;
 
         let mut aapt = self.0.build_tool(bin!("aapt"))?;
-        aapt.arg("add").arg(self.0.unaligned_apk()).arg(format!(
-            "lib/{}/{}",
-            abi,
-            file_name.to_str().unwrap()
-        ));
+        aapt.arg("add").arg(self.0.unaligned_apk()).arg(&lib_path);
         if !aapt.status()?.success() {
             return Err(NdkError::CmdFailed(aapt));
         }

ndk-macro/src/helper.rs

@@ -49,16 +49,11 @@ fn crate_name(name: &str) -> Result<String> {
 pub fn crate_path(name: &str, overridden_path: &Option<Path>) -> Path {
     // try to use overridden crate path
     overridden_path.clone().unwrap_or_else(|| {
-        // the binding to hold string from `crate_name` fn
-        let mut detected_name = None;
         Ident::new(
             // try to determine crate name from Cargo.toml
             crate_name(name)
                 .ok()
-                .map(|name| {
-                    detected_name = Some(name);
-                    detected_name.as_ref().unwrap().as_str()
-                })
+                .as_deref()
                 // or use default crate name
                 // (this may cause compilation error when crate is not found)
                 .unwrap_or_else(|| name),