Ensure protoc is installed for release CI (sigp#3621)

## Issue Addressed

The release CI is currently broken due to the addition of the `protoc` dependency. Here's a failure of the release flow running on my fork: https://github.com/michaelsproul/lighthouse/actions/runs/3155541478/jobs/5134317334

## Proposed Changes

- Install `protoc` on Windows and Mac so that it's available for `cargo install`.
- Install an x86_64 binary in the Cross image for the aarch64 platform: we need a binary that runs on the host, _not_ on the target.
- Fix `macos` local testnet CI by using the Github API key to dodge rate limiting (this issue: actions/runner-images#602).

.github/workflows/local-testnet.yml

@@ -22,6 +22,8 @@ jobs:
         run: rustup update stable
       - name: Install Protoc
         uses: arduino/setup-protoc@v1
+        with:
+            repo-token: ${{ secrets.GITHUB_TOKEN }}
       - name: Install ganache
         run: npm install ganache@latest --global
 

.github/workflows/release.yml

@@ -83,6 +83,15 @@ jobs:
               if: startsWith(matrix.arch, 'x86_64-windows')
               run: echo "LIBCLANG_PATH=$((gcm clang).source -replace "clang.exe")" >> $env:GITHUB_ENV
 
+            # ==============================
+            # Windows & Mac dependencies
+            # ==============================
+            - name: Install Protoc
+              if: contains(matrix.arch, 'darwin') || contains(matrix.arch, 'windows')
+              uses: arduino/setup-protoc@v1
+              with:
+                repo-token: ${{ secrets.GITHUB_TOKEN }}
+
             # ==============================
             #       Builds
             # ==============================

Cross.toml

@@ -1,5 +1,5 @@
 [target.x86_64-unknown-linux-gnu]
-dockerfile = './scripts/cross/x86_64-unknown-linux-gnu.dockerfile'
+dockerfile = './scripts/cross/Dockerfile'
 
 [target.aarch64-unknown-linux-gnu]
-dockerfile = './scripts/cross/aarch64-unknown-linux-gnu.dockerfile'
+dockerfile = './scripts/cross/Dockerfile'

lcli/Dockerfile

@@ -2,7 +2,7 @@
 #  - from the `lighthouse` dir with the command: `docker build -f ./lcli/Dockerflie .`
 #  - from the current directory with the command: `docker build -f ./Dockerfile ../`
 FROM rust:1.62.1-bullseye AS builder
-RUN apt-get update && apt-get -y upgrade && apt-get install -y cmake libclang-dev
+RUN apt-get update && apt-get -y upgrade && apt-get install -y cmake libclang-dev protobuf-compiler
 COPY . lighthouse
 ARG PORTABLE
 ENV PORTABLE $PORTABLE