Skip compilation on TruffleRuby

* Running libv8 on GraalVM LLVM is unlikely to ever work, instead using
  Graal.js makes more sense. This is already the case in mini_racer.
  libv8-node is a necessary dependency of mini_racer on CRuby, so for
  TruffleRuby the extconf.rb simply creates a dummy Makefile.

Author: eregon

.github/workflows/build.yml

@@ -25,6 +25,16 @@ jobs:
        run: apt-get update && apt-get install -y shellcheck
      - name: Shellcheck
        run: shellcheck libexec/*
+  compile-truffleruby:
+    name: Compile on truffleruby
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: truffleruby
+          bundler-cache: true
+      - run: bundle exec rake compile
   build-ruby:
     name: Build (ruby)
     outputs:

ext/libv8-node/extconf.rb

@@ -1,6 +1,12 @@
 # frozen_string_literal: true
 
 require 'mkmf'
+
+if RUBY_ENGINE == "truffleruby"
+  File.write("Makefile", dummy_makefile($srcdir).join(""))
+  return
+end
+
 create_makefile('libv8-node')
 
 require File.expand_path('location', __dir__)