chore: fix building ffi bindings on macOS

packages/p2panda/native/build.rs

@@ -5,14 +5,21 @@ use std::env;
 /// Pinned NDK version, needs to be installed on machine.
 const ANDROID_NDK_VERSION: &'static str = "25.2.9519653";
 
-/// x86-64 linux standard library path inside NDK directory.
-const LINUX_X86_64_LIB_DIR: &'static str =
-    "/toolchains/llvm/prebuilt/linux-x86_64/lib64/clang/14.0.7/lib/linux/";
-
 fn main() {
     let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
     let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
 
+    let host_os_prefix = if env::consts::OS == "macos" {
+        "darwin"
+    } else {
+        "linux"
+    };
+
+    // x86-64 linux standard library path inside NDK directory.
+    let linux_x86_64_lib_dir = std::format!(
+        "/toolchains/llvm/prebuilt/{host_os_prefix}-x86_64/lib64/clang/14.0.7/lib/linux/"
+    );
+
     // The new NDK doesn't link to `libgcc` anymore, which breaks our our libraries since they
     // depended on the symbols from `libclang_rt.builtins-x86_64-android` like `__extenddftf2`. See
     // https://github.com/bbqsrc/cargo-ndk/issues/94 for details.
@@ -21,7 +28,7 @@ fn main() {
     // `libclang_rt.builtins-x86_64-android` library in this case.
     if target_arch == "x86_64" && target_os == "android" {
         let android_home = env::var("ANDROID_HOME").expect("ANDROID_HOME not set");
-        println!("cargo:rustc-link-search={android_home}/ndk/{ANDROID_NDK_VERSION}/{LINUX_X86_64_LIB_DIR}");
+        println!("cargo:rustc-link-search={android_home}/ndk/{ANDROID_NDK_VERSION}/{linux_x86_64_lib_dir}");
         println!("cargo:rustc-link-lib=static=clang_rt.builtins-x86_64-android");
     }
 }