Implement a more robust way of locating rust-analyzer

When bundled, we will retrieve it out of the `Resources` folder.
Locally, we're expected to run `script/download-rust-analyzer` and
put `vendor/bin` in our $PATH.

script/download-rust-analyzer

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+set -e
+
+export RUST_ANALYZER_URL="https://github.com/rust-analyzer/rust-analyzer/releases/download/2021-10-18/"
+
+function download {
+    local filename="rust-analyzer-$1"
+    curl -L $RUST_ANALYZER_URL/$filename.gz | gunzip > vendor/bin/$filename
+    chmod +x vendor/bin/$filename
+}
+
+mkdir -p vendor/bin
+download "x86_64-apple-darwin"
+download "aarch64-apple-darwin"