message: Gitian: fix check path and detached signatures dir name
  previous setting checked for ion folder instead of pivx
  previous setting checked for ion detached signatures instead of
diff: @@ -24,11 +24,11 @@ def setup():
  subprocess.check_call(['sudo', 'apt-get', 'install', '-qq'] + programs)
  if not os.path.isdir('gitian.sigs'):
  subprocess.check_call(['git', 'clone', 'https://github.com/PIVX-Project/gitian.sigs.git'])
  - if not os.path.isdir('ion-detached-sigs'):
  + if not os.path.isdir('PIVX-detached-sigs'):
  subprocess.check_call(['git', 'clone', 'https://github.com/PIVX-Project/PIVX-detached-sigs.git'])
  if not os.path.isdir('gitian-builder'):
  subprocess.check_call(['git', 'clone', 'https://github.com/devrandom/gitian-builder.git'])
  - if not os.path.isdir('ion'):
  + if not os.path.isdir('PIVX'):
  subprocess.check_call(['git', 'clone', 'https://github.com/PIVX-Project/PIVX.git'])
  os.chdir('gitian-builder')
  make_image_prog = ['bin/make-base-vm', '--suite', 'bionic', '--arch', 'amd64']
  