.github: build native gem

Build a native gem with pre-compiled .so files so that users wouldn't
have to install the Rust compiler and everything else.

.github/workflows/build_release_pipeline.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Build gem
         if: success() && github.ref == 'refs/heads/master'
         run: |
-          gem build prometheus-client-mmap.gemspec
+          bundle exec rake gem:x86_64-linux
           echo "::set-output name=gem_version::v$(bundle exec rake version)"
       - name: Release to rubygems
         if: success() && github.ref == 'refs/heads/master'
@@ -35,7 +35,7 @@ jobs:
           touch $HOME/.gem/credentials
           chmod 600 $HOME/.gem/credentials
           printf -- "---\n:rubygems_api_key: ${GEM_HOST_API_KEY}\n" > $HOME/.gem/credentials
-          gem push vinted-prometheus-client-mmap-*.gem -V
+          gem push pkg/vinted-prometheus-client-mmap-*.gem -V
         env:
           GEM_HOST_API_KEY: "${{ secrets.RUBYGEMS_AUTH_TOKEN }}"
       - name: Tag repo with new gem version

Rakefile

@@ -72,6 +72,12 @@ namespace "gem" do
       ENV["RCD_IMAGE"] = "rbsys/#{plat}:#{RbSys::VERSION}"
 
       RakeCompilerDock.sh <<~SH, platform: plat
+        (mkdir "$HOME/.protoc") ||: &&
+        curl -L https://github.com/protocolbuffers/protobuf/releases/download/v24.4/protoc-24.4-linux-x86_64.zip -o "$HOME/.protoc/protoc-24.4-linux-x86_64.zip" &&
+        cur="$(pwd)" &&
+        cd "$HOME/.protoc"; unzip -o protoc-24.4-linux-x86_64.zip &&
+        cd "$cur" &&
+        export PATH="${PATH}:$HOME/.protoc/bin" &&
         bundle && \
         RUBY_CC_VERSION="#{cross_rubies.join(":")}" \
         rake native:#{plat} pkg/#{gemspec.full_name}-#{plat}.gem