Add example configuration for rotating GC log
By default, the JVM GC log file grows without
limitation. This is inconvenient for a long running
process like Elasticsearch.
With this commit we add an example configuration
for a rotating GC log in `conig/jvm.options`.
# log GC status to a file with time stamps
# ensure the directory exists
#-Xloggc:${loggc}
+
+# By default, the GC log file will not rotate.
+# By uncommenting the lines below, the GC log file
+# will be rotated every 128MB at most 32 times.
+#-XX:+UseGCLogFileRotation
+#-XX:NumberOfGCLogFiles=32
+#-XX:GCLogFileSize=128M
