misc/50119: MKREPRO: get repeatable timestamps for output files

[Thomas Klausner <wiz%NetBSD.org@localhost>]

>Number:         50119
>Category:       misc
>Synopsis:       MKREPRO: get repeatable timestamps for output files
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    misc-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Aug 03 14:00:00 +0000 2015
>Originator:     Thomas Klausner
>Release:        NetBSD 7.99.20
>Organization:
Curiosity is the very basis of education and if you tell me that 
curiosity killed the cat, I say only that the cat died nobly.
- Arnold Edinborough
>Environment:
	
	
Architecture: x86_64
Machine: amd64
>Description:
Found in the debian MKREPRO builds for NetBSD:
When using the same tree to build on different dates, you will get different *.tgz
files since the created files get the current timestamp at the time of the build.

This makes consecutive builds of the same tree differ.
>How-To-Repeat:
Build the same tree now and five minutes/hours/days later.
See that base.tgz for the two builds is not the same.
>Fix:
A number of solutions are possible (from IRC), e.g.:
* make the output timestamp the date of the newest used input file
* use a fixed time stamp for a build, e.g.
  MKREPROTIMESTAMP=20150802T151413.12+0000
  either by touch(1)ing the files, or by making tar(1) use a fixed
  date for all files it includes

>Unformatted: