RFR: 8293499: Provide jmod --compress option [v5]

[Aleksey Shipilev]

On Tue, 13 Sep 2022 16:51:52 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   More review comments
>
> src/jdk.jlink/share/classes/jdk/tools/jmod/resources/jmod.properties line 87:
> 
>> 85: main.opt.compress=Compression to use when creating the JMOD archive.\
>> 86: \ Accepted values are: zip-[0-9], where zip-0 provides no compression, and zip-9\
>> 87: \ provides the best compression.
> 
> Should specify the default if not set.

Here is where we get into a minor pickle. We currently default to `Deflater.DEFAULT_COMPRESSION`, which is `-1`, and which is handled inside `zlib` as `6`. We can say `zip-6` here is the default, but that would be stale if zlib ever updates its default. Still fair to say `zip-6` here, or?

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PR: https://git.openjdk.org/jdk/pull/10213