misc/57913: [RB] acorn32/earmv4 mksparkive.sh: Don't embed build timestamp into archive

[jbglaw%lug-owl.de@localhost]

>Number:         57913
>Category:       misc
>Synopsis:       [RB] acorn32/earmv4 mksparkive.sh: Don't embed build timestamp into archive
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    misc-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Feb 09 06:55:00 +0000 2024
>Originator:     Jan-Benedict Glaw
>Release:        current
>Organization:
>Environment:
>Description:
Comparing CI builds, I found that acorn32 builds use a specific script to generate an archive. This contains the compiled file's mtimes, which breaks reproducible builds
>How-To-Repeat:
Build twice for acorn32/earmv4 and observe differences in build artifacts.
>Fix:
index 3a21e231d2e8..d2131b7b7d48 100755
--- a/distrib/acorn32/mksparkive.sh
+++ b/distrib/acorn32/mksparkive.sh
@@ -89,6 +89,7 @@ makeheader()
        # extracting only the length here.
        length=`wc -c "$filename"`
        eval `${TOOL_STAT} -s "$statfilename"`
+       [ -n "${MKREPRO_TIMESTAMP}" ] && st_mtime=${MKREPRO_TIMESTAMP}
        # centiseconds since 1st Jan 1900
        timestamp=`expr $st_mtime \* 100 + 220898880000`
        lowtype=`echo "$filetype" | sed s/.//`