binman: Use binary mode when compressing data

The lz4 utility inserts binary data in its output which cannot always be
converted to unicode (nor should it be). Fix this by using the new binary
mode for program output.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/binman/ftest.py

@@ -1557,7 +1557,7 @@ class TestFunctional(unittest.TestCase):
         out = os.path.join(self._indir, 'lz4.tmp')
         with open(out, 'wb') as fd:
             fd.write(data)
-        return tools.Run('lz4', '-dc', out)
+        return tools.Run('lz4', '-dc', out, binary=True)
         '''
         try:
             orig = lz4.frame.decompress(data)