4487. [test] Make system tests work on Windows. [RT #42931]

bin/tests/system/sfcache/prereq.sh

@@ -6,9 +6,12 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-../../../tools/genrandom 400 random.data
+SYSTEMTESTTOP=..
+. $SYSTEMTESTTOP/conf.sh
 
-if $KEYGEN -q -a RSAMD5 -b 512 -n zone -r random.data foo > /dev/null 2>&1
+$GENRANDOM 400 $RANDFILE
+
+if $KEYGEN -q -a RSAMD5 -b 512 -n zone -r $RANDFILE foo > /dev/null 2>&1
 then
     rm -f Kfoo*
 else