do not try to isolate x11 on build.kde

it manages its own x11 and attempts to isolate yourself is an endless waste
of time of issues

drkonqi/tests/integration/suite

@@ -50,6 +50,19 @@ class XvfbIsolator
   end
 end
 
+class NoIsolator
+  def run(cmd)
+    warn cmd.to_s
+    system(cmd) || raise
+  end
+end
+
+def isolator
+    return NoIsolator.new if ENV['JENKINS_SERVER_COOKIE'] || ENV['NO_ISOLATOR']
+    return XephyrIsolator.new if ENV['XEPHYR']
+    XvfbIsolator.new
+end
+
 OptionParser.new do |opts|
   opts.banner = "Usage: #{$0} ARGS"
 
@@ -75,7 +88,6 @@ Dir.mktmpdir do |tmpdir|
   ENV['HOME'] = tmpdir
   ENV.keys.each { |k| ENV.delete(k) if k.start_with?('XDG_') }
   Dir.glob("#{__dir__}/*_test.rb").each do |test|
-    isolator = ENV['XEPHYR'] ? XephyrIsolator.new : XvfbIsolator.new
     isolator.run("dbus-run-session -- ruby '#{test}' -p")
   end
   sleep 2 # Wait a bit to make sure all children are dead.