[tex-live] Fixed compilation date in the .log file

[Joseph Wright]

On 05/04/2018 21:23, Akira Kakuto wrote:
>> I guess this is done on purpose by the l3build system to avoid
>> differences when checking regression files.  I had never noticed this
>> before :-(
> 
> Many thanks. I didn't know that. I can find in
> l3build-aux.lua:
> 
> function setepoch()
>   return
>     os_setenv .. " SOURCE_DATE_EPOCH=" .. epoch
>       .. os_concat ..
>     os_setenv .. " SOURCE_DATE_EPOCH_TEX_PRIMITIVES=1"
>       .. os_concat ..
>     os_setenv .. " FORCE_SOURCE_DATE=1"
>       .. os_concat
> end
> 
> Best,
> Akira

We've recently adjusted the defaults so the above doesn't apply 
as-standard to documentation typesetting.

Joseph