RFR: 7903871: Typo bug in doc/building.md of 'Rebuilding faster'

[SendaoYan]

On Mon, 21 Oct 2024 08:23:03 GMT, SendaoYan <syan at openjdk.org> wrote:

> Hi all,
> The document of `doc/building.md` at chapter `Rebuilding faster with build/make.sh` has a typo bug, which may cause misunderstand.
> Anyone wants to skip download dependencies, the option `--skip-download` should passed to `make/build.sh` explicitly. Because the default valune of variable `SKIP_DOWNLOAD` in [build-common.sh](https://github.com/openjdk/jtreg/blob/master/make/build-support/build-common.sh#L155) is empty, unless execute `make/build.sh` with `--skip-download` option.
> Only fix the document bug, no risk.

The GHA report `Installed distributions` failure, it's environmental issue, unreleated to this PR.

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PR Comment: https://git.openjdk.org/jtreg/pull/232#issuecomment-2425969561