Fix gitaly install on systems where env doesn't support the -u flag

At least on OpenBSD, /usr/bin/env doesn't support the -u flag
and bails out. So first check if env supports it, and only use it,
when it supports it.

This makes installing gitaly work for me on OpenBSD.

lib/tasks/gitlab/gitaly.rake

@@ -15,8 +15,7 @@ Usage: rake "gitlab:gitaly:install[/installation/dir,/storage/path]")
 
       checkout_or_clone_version(version: version, repo: args.repo, target_dir: args.dir)
 
-      command = %w[/usr/bin/env -u RUBYOPT -u BUNDLE_GEMFILE]
-
+      command = []
       _, status = Gitlab::Popen.popen(%w[which gmake])
       command << (status.zero? ? 'gmake' : 'make')
 
@@ -31,7 +30,7 @@ Usage: rake "gitlab:gitaly:install[/installation/dir,/storage/path]")
       Dir.chdir(args.dir) do
         # In CI we run scripts/gitaly-test-build instead of this command
         unless ENV['CI'].present?
-          Bundler.with_original_env { run_command!(command) }
+          Bundler.with_original_env { Gitlab::Popen.popen(command, nil, { "RUBYOPT" => nil, "BUNDLE_GEMFILE" => nil }) }
         end
       end
     end

spec/tasks/gitlab/gitaly_rake_spec.rb

@@ -53,8 +53,6 @@ describe 'gitlab:gitaly namespace rake task' do
     end
 
     describe 'gmake/make' do
-      let(:command_preamble) { %w[/usr/bin/env -u RUBYOPT -u BUNDLE_GEMFILE] }
-
       before do
         stub_env('CI', false)
         FileUtils.mkdir_p(clone_path)
@@ -69,7 +67,7 @@ describe 'gitlab:gitaly namespace rake task' do
 
         it 'calls gmake in the gitaly directory' do
           expect(Gitlab::Popen).to receive(:popen).with(%w[which gmake]).and_return(['/usr/bin/gmake', 0])
-          expect(main_object).to receive(:run_command!).with(command_preamble + %w[gmake]).and_return(true)
+          expect(Gitlab::Popen).to receive(:popen).with(%w[gmake], nil, { "BUNDLE_GEMFILE" => nil, "RUBYOPT" => nil }).and_return(true)
 
           subject
         end
@@ -82,7 +80,7 @@ describe 'gitlab:gitaly namespace rake task' do
         end
 
         it 'calls make in the gitaly directory' do
-          expect(main_object).to receive(:run_command!).with(command_preamble + %w[make]).and_return(true)
+          expect(Gitlab::Popen).to receive(:popen).with(%w[make], nil, { "BUNDLE_GEMFILE" => nil, "RUBYOPT" => nil }).and_return(true)
 
           subject
         end
@@ -99,7 +97,7 @@ describe 'gitlab:gitaly namespace rake task' do
           end
 
           it 'calls make in the gitaly directory with --no-deployment flag for bundle' do
-            expect(main_object).to receive(:run_command!).with(command_preamble + command).and_return(true)
+            expect(Gitlab::Popen).to receive(:popen).with(command, nil, { "BUNDLE_GEMFILE" => nil, "RUBYOPT" => nil }).and_return(true)
 
             subject
           end