docs: improve make with parallel jobs description. #21942

Changed use -jX here for parallelism to use "-j N" for N parallel jobs

Rationale: In my opinion use -jX here for parallelism is quite ambiguous as it could be perceived as a single option without any argument. Ie running:

make -jX

Embarrassingly this caused me to be stuck for quite a long time until I opened the help menu for make but if I am the only one who faced this issue I would be happy to close this PR.

ACK, agree that this is a clearer wording.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #20610 (doc: update for NetBSD 9.1, add GUI Build Instructions by jarolrod)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

Concept ACK

Two more places where you might want to add a similar note:

• https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md#to-build
• https://github.com/bitcoin/bitcoin/blob/master/doc/build-windows.md#building-for-64-bit-windows

Concept ACK

Two more places where you might want to add a similar note:

• https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md#to-build
• https://github.com/bitcoin/bitcoin/blob/master/doc/build-windows.md#building-for-64-bit-windows

Thanks for pointing that out. Updated the PR according to this.

ACK 07bc22ef105dee3c6c465a3ef31e52fd198e786d