Set root dir in lint project.xml

Set the root dir in the project.xml for lint so that the paths in the
lint report are relative to the top of the tree instead of relative
to the project.xml.

Bug: 153485543
Test: run lint
Change-Id: Ie163a4dadd976e708f798855de73e58084931a91

scripts/lint-project-xml.py

@@ -77,6 +77,8 @@ def parse_args():
                       help='mark the module as a test.')
   parser.add_argument('--cache_dir', dest='cache_dir',
                       help='directory to use for cached file.')
+  parser.add_argument('--root_dir', dest='root_dir',
+                      help='directory to use for root dir.')
   group = parser.add_argument_group('check arguments', 'later arguments override earlier ones.')
   group.add_argument('--fatal_check', dest='checks', action=check_action('fatal'), default=[],
                      help='treat a lint issue as a fatal error.')
@@ -162,6 +164,8 @@ def write_project_xml(f, args):
 
   f.write("<?xml version='1.0' encoding='utf-8'?>\n")
   f.write("<project>\n")
+  if args.root_dir:
+    f.write("  <root dir='%s' />\n" % args.root_dir)
   f.write("  <module name='%s' android='true' %sdesugar='full' >\n" % (args.name, "library='true' " if args.library else ""))
   if args.manifest:
     f.write("    <manifest file='%s' %s/>\n" % (args.manifest, test_attr))