libsdl2 built fails when updating ffmpeg

[tome at qx.net]

>
>> On Mar 22, 2017, at 22:56, tome at qx.net wrote:
>>
>> Mac mini 2.7Ghz Intel Core i7
>> 8 GB 1333 Mhz DDR3
>> Lion OS X 10.7.5
>> ffmpeg @3.1.4_0+gpl2+x11 (active)
>>
>> After successfully patching a libarchive failure, the ffmpeg update
>> continued with a failure during libsdl2 build.  I captured the log and
>> then did the suggested 'sudo port clean libsdl2' and then 'sudo port
>> update outdated', which failed again, and I captured that log also.  I
>> then did the suggested 'sudo port uninstall libsdl2' and again did 'sudo
>> port update outdated', again with a libsdl2 failure.  I have attached
>> the
>> last log, the other two are available if necessary.  I searched the
>> archive, but found nothing related to this failure.  Please advise if
>> this
>> should be a ticket.  Thank you, Tom
>> <libsdl2b-main.log>
>
> The errors in the log are:
>
> use of undeclared identifier
> 'NSWindowDidChangeBackingPropertiesNotification'
>
> and:
>
> use of undeclared identifier 'NSBackingPropertyOldScaleFactorKey'
>
> These errors are mentioned further down in this ticket:
>
> https://trac.macports.org/ticket/52210#comment:9
>
> That ticket is about how libsdl2 does not build on 10.6 without the 10.7
> SDK. But you're on 10.7 so you already have the 10.7 SDK so this doesn't
> quite fit.
>
> What version of Xcode and the command line tools do you have installed? If
> it's not the very latest for 10.7 (Xcode 4.6.3 and Command Line Tools (OS
> X Lion) for Xcode - April 2013) try updating to that.
>
>

Thank you.  I am downloading xcode 4.6.3.  I have not been able to
determine my version of command line tools. Where on my mac do I check the
version of command line tools?  Are there things I should backup before
starting these upgrades?