8141439: Fix compare.sh -o <otherdir> (broken by JDK-8136813)

Reviewed-by: tbell, erikj

common/autoconf/compare.sh.in

@@ -86,4 +86,6 @@ fi
 $RM $OUTPUT_ROOT/compare.log.old 2> /dev/null
 $MV $OUTPUT_ROOT/compare.log $OUTPUT_ROOT/compare.log.old 2> /dev/null
 
+export SCRIPT_DIR="$( cd "$( dirname "$0" )" > /dev/null && pwd )"
+
 $BASH $SRC_ROOT/common/bin/logger.sh $OUTPUT_ROOT/compare.log $BASH "$REAL_COMPARE_SCRIPT" "$@"

common/bin/compare.sh

@@ -989,7 +989,7 @@ if [ "$OPENJDK_TARGET_OS" = "windows" ]; then
     fi
 fi
 
-THIS="$( cd "$( dirname "$0" )" > /dev/null && pwd )"
+THIS="$SCRIPT_DIR"
 echo "$THIS"
 THIS_SCRIPT="$0"