RFR: 6889: Provide build script for making it easier to build JMC [v4]

[Schalli1987]

On Wed, 16 Sep 2020 08:00:36 GMT, Marcus Hirt <hirt at openjdk.org> wrote:

>> Which version of ps do you use?
>> I have
>> $ ps --version
>> ps from procps-ng 3.3.16
>> The `--ppid` option was added in 3.1.6 back in 2003?
>
>> Which version of ps do you use?
> 
> This is the Mac version of ps, which seems to have slightly different parameter set. I'm running on Catalina 10.15.6.

Tried another way to terminate jetty server, please check again.

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PR: https://git.openjdk.java.net/jmc/pull/100