vimPlugins.blink-cmp: fix darwin build

Follow the linker args that upstream uses for darwin
https://github.com/saghen/blink.cmp/blob/main/.cargo/config.toml

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

pkgs/applications/editors/vim/plugins/non-generated/blink-cmp/default.nix

@@ -26,6 +26,8 @@ let
     env = {
       # TODO: remove this if plugin stops using nightly rust
       RUSTC_BOOTSTRAP = true;
+      # Allow undefined symbols on Darwin - they will be provided by Neovim's LuaJIT runtime
+      RUSTFLAGS = lib.optionalString stdenv.hostPlatform.isDarwin "-C link-arg=-undefined -C link-arg=dynamic_lookup";
     };
   };
 in