Add a script for running the benchmarks with or without jbigi

benchmarks/benchmark.sh

+#!/bin/sh
+
+CWD=$(dirname "$0")
+if [ "x$JBIGI" = 'x' ]
+then
+    JBIGI="$CWD/../build/jbigi.jar"
+fi
+if [ "x$JAVA" = 'x' ]
+then
+    JAVA=java
+fi
+
+CLASSPATH="$CWD/java/build/benchmarks.jar"
+if [ "x${1:-}" = 'x--jbigi' ]
+then
+    CLASSPATH="$CLASSPATH:$JBIGI"
+    shift
+fi
+
+$JAVA -cp "$CLASSPATH" org.openjdk.jmh.Main "$@"