RFR: 8339335: set number of parallel jobs when building webkit [v2]

[Kevin Rushforth]

On Tue, 3 Sep 2024 19:56:48 GMT, Johan Vos <jvos at openjdk.org> wrote:

>> When building webkit, the perl script in `modules/javafx.web/src/main/native/Tools/Scripts/build-webkit` will check for a `-j` argument in `$makeArgs`. If that doesn't exist, it will default to `numberOfCPUs()`.
>> This PR passes the `NUM_COMPILE_THREADS` from `build.gradle` to the `build-webkit` script. When not setting `NUM_COMPILE_THREADS` explicitly,it will default to the number of CPU's as well, hence it will have the same behavior as without this PR.
>> When setting `NUM_COMPILE_THREADS` explicitly, the provided number will be used by cmake as well now.
>
> Johan Vos has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove the special case where native compile jobs are hard set to 1
>   on Mac -- see JDK-8339505

This setting (nor likely any setting we can, or would want to, control) doesn't affect the parallelism of an individual clang process, but rather controls the maximum number of concurrent clang processes that will be launched.

The net effect of this patch on macOS should be that we will now do parallel compilation for native code in the graphics module by default. There should be no change, by default, in the parallelism of WebKit compilation (there would have been before the most recent commit that Johan did).

What this patch will do is to apply the same `NUM_COMPILE_THREADS` flag to native WebKit as well as native graphics compilation. Prior to this fix, setting `NUM_COMPILE_THREADS` to, say 2, would have been used for the graphics build and ignored for the WebKit build.

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PR Comment: https://git.openjdk.org/jfx/pull/1554#issuecomment-2327399993