Fix bundler env being copied to Ruby runner

Fix issues with the wrong bundle of gems being used as context for the
runner. This failed to find the Ruby gem as it was using this project's
test suite Gemfile instead.

Wrap commands with `Bundler.with_unbundled_env` so it removes any
Bundler context from the environment. It also clears some other env
vars, so explicitly set them again in the base `run_env` method.

ruby/Gemfile.lock

@@ -1,13 +1,13 @@
 PATH
   remote: ../../../..
   specs:
-    appsignal (3.0.15)
+    appsignal (3.9.2)
       rack
 
 GEM
   remote: https://rubygems.org/
   specs:
-    rack (2.2.3)
+    rack (3.1.5)
 
 PLATFORMS
   ruby

spec/support/runner.rb

@@ -91,31 +91,41 @@ def install_report?
   end
 
   def run_env
-    { "APPSIGNAL_PUSH_API_KEY" => @push_api_key }
+    {
+      "APPSIGNAL_PUSH_API_KEY" => @push_api_key,
+      "APPSIGNAL_PUSH_API_ENDPOINT" => ENV["APPSIGNAL_PUSH_API_ENDPOINT"],
+      "APPSIGNAL_DIAGNOSE_ENDPOINT" => ENV["APPSIGNAL_DIAGNOSE_ENDPOINT"]
+    }
   end
 
   def run_command(_arguments)
     raise NotImplementedError, "`Runner` subclasses must implement `run_command`"
   end
 
   def run # rubocop:disable Metrics/MethodLength
-    Dir.chdir directory do
-      before_setup
-      setup_commands.each do |command|
-        run_setup command
+    Bundler.with_unbundled_env do
+      Dir.chdir directory do
+        before_setup
+        setup_commands.each do |command|
+          run_setup command
+        end
+        after_setup
       end
-      after_setup
     end
 
     # Run the command
     prompt = @prompt ? %(echo "#{@prompt}" | ) : ""
     command = run_command(@arguments.dup)
     read, write = IO.pipe
-    pid = spawn(
-      run_env,
-      "#{prompt} #{command}",
-      { [:out, :err] => write, :chdir => directory }
-    )
+    env = run_env
+    pid =
+      Bundler.with_unbundled_env do
+        spawn(
+          env,
+          "#{prompt} #{command}",
+          { [:out, :err] => write, :chdir => directory }
+        )
+      end
     _pid, status = Process.wait2 pid # Wait until command exits
     write.close