Do not show python stack trace in ninja.py when KeyboardInterrupt happens

Before
```
❯ ninja -C out/Default
ninja: Entering directory `out/Default'
Traceback (most recent call last):
  File "/Users/jwata/depot_tools/ninja.py", line 85, in <module>
    sys.exit(main(sys.argv))
  File "/Users/jwata/depot_tools/ninja.py", line 79, in main
    return subprocess.call([ninja_path] + args[1:])
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/subprocess.py", line 351, in call
    return p.wait(timeout=timeout)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/subprocess.py", line 1189, in wait
    return self._wait(timeout=timeout)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/subprocess.py", line 1917, in _wait
    (pid, sts) = self._try_wait(0)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/subprocess.py", line 1875, in _try_wait
    (pid, sts) = os.waitpid(self.pid, wait_flags)
KeyboardInterrupt
```

After
```
❯ ninja -C out/Default
ninja: Entering directory `out/Default'
interrupted
```

Fixed: 1398687
Change-Id: I7cbc80f2214d46b492c6e9ade7b0d78766a8a6f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4085366
Reviewed-by: Nico Weber <thakis@chromium.org>
Auto-Submit: Junji Watanabe <jwata@google.com>
Commit-Queue: Junji Watanabe <jwata@google.com>

ninja.py

@@ -82,4 +82,7 @@ def main(args):
 
 
 if __name__ == '__main__':
-  sys.exit(main(sys.argv))
+  try:
+    sys.exit(main(sys.argv))
+  except KeyboardInterrupt:
+    sys.exit(1)