utils/tdiff.py: Don't parse duplicate targets

[luke]

Summary

When diffing a large target like all, most of the entries in the target
list in query_ninja are duplicated. I haven't looked that closely as to
why this is the case, but uniquing the list brought the size of it down
from 21781 to 76 for me.

[MatzeB]

LGTM

utils/tdiff.py

84

[luke]

Thanks for writing this script btw, it's really handy :)

utils/tdiff.py

def parse(text):
 
     if target is not None:
         yield Node(inputs, rule, target, outputs)
 
 
 def query_ninja(targets, cwd):
     # Query ninja for a node in its build dependency tree.
     proc = subprocess.Popen(
-        ["ninja", "-t", "query"] + targets,
+        ["ninja", "-t", "query", *set(targets)],
         cwd=cwd,
         stdout=subprocess.PIPE,
         universal_newlines=True,
     )
     out, _ = proc.communicate()
     if proc.returncode != 0:
         raise Exception("Failed to query ninja for targets: %s" % (targets,))
     return parse(out)