File reproducible.patch of Package opa-fm

https://github.com/01org/opa-fm/pull/9
https://bugzilla.opensuse.org/show_bug.cgi?id=1047218

commit 8b1b100a34f6a03ab719fa0602f60b97be05ec9b
Author: Bernhard M. Wiedemann <bwiedemann@suse.de>
Date:   Mon Jul 24 07:50:23 2017 +0200

    Use SOURCE_DATE_EPOCH to override build date
    
    to make reproducible builds of opa-fm packages easier
    e.g. for openSUSE
    
    See https://reproducible-builds.org/ for why this is good
    and https://reproducible-builds.org/specs/source-date-epoch/
    for the definition of this variable.

diff --git a/MakeTools/prep.sh b/MakeTools/prep.sh
index c0a4bd1..c4b7fec 100755
--- a/MakeTools/prep.sh
+++ b/MakeTools/prep.sh
@@ -81,7 +81,10 @@ then
 	exit 1
 fi
 
-DATE=${DATE:-"`date +'%m/%d/%y %H:%M'`"}
+DATE_FMT='%m/%d/%y %H:%M'
+[ -z "$SOURCE_DATE_EPOCH" ] ||\
+       DATE=${DATE:-"`date -u -d@$SOURCE_DATE_EPOCH "+$DATE_FMT"`"}
+DATE=${DATE:-"`date "+$DATE_FMT"`"}
 
 if [ "$#" = 1 ]
 then