install/50361: MKREPRO: time stamps in installation ISO

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

>Number:         50361
>Category:       install
>Synopsis:       MKREPRO: time stamps in installation ISO
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Oct 23 08:05:00 +0000 2015
>Originator:     Thomas Klausner
>Release:        NetBSD 7.99.21
>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:
In a MKREPRO build, the time stamps of files in an installation ISO
file (like amd64/installation/cdrom/boot-com.iso) has the current date.

This makes the build from the same source on different dates produce
different results.
>How-To-Repeat:
Build a distribution with MKREPRO from the same source on different dates.
>Fix:
Use the date of the source files for the files inside the ISO;
or use SOURCE_DATE_EPOCH (see https://reproducible-builds.org/specs/source-date-epoch/).