bug#28571: 25.3; Compile error on macOS Sierra

[YAMAMOTO Mitsuharu]

>>>>> On Sun, 24 Sep 2017 07:49:55 +0000, Philipp Stephani 
>>>>> <p.stephani2@gmail.com> said:

>> I take it you upgraded Xcode the other day? (To version 9, I
>> think?)
>> 

> Yes, indeed.

Probably You need to execute "$ xcode-select --install" to install
Command Line Tools for Xcode.  You can actually go without it by
tweaking some environment variables and/or compiler arguments, but I
wouldn't recommend that unless you have a shortage of disk space and
you really understand what you are doing.

                                     YAMAMOTO Mitsuharu
                                mituharu@math.s.chiba-u.ac.jp