gclient: setdep writes binary for windows newline support

This fixes an issue on Windows where running `gclient setdep` would convert the DEPS file from LF to CRLF line endings.

From the python 2.7 docs:

" On Windows, 'b' appended to the mode opens the file in binary mode, so there are also modes like 'rb', 'wb', and 'r+b'. Python on Windows makes a distinction between text and binary files; the end-of-line characters in text files are automatically altered slightly when data is read or written. "

- https://docs.python.org/2.7/tutorial/inputoutput.html#reading-and-writing-files

Change-Id: I94183918789a8cdd4aa655db4b3dadfaae23d13a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2067477
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: John Emau <John.Emau@microsoft.com>

gclient.py

@@ -2981,8 +2981,8 @@ def CMDsetdep(parser, args):
     else:
       gclient_eval.SetRevision(local_scope, name, value)
 
-  with open(options.deps_file, 'w') as f:
-    f.write(gclient_eval.RenderDEPSFile(local_scope))
+  with open(options.deps_file, 'wb') as f:
+    f.write(gclient_eval.RenderDEPSFile(local_scope).encode('utf-8'))
 
 
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