RFR: 7903936: Update variable names in build.sh documentation [v3]

[Oleksii Sylichenko]

> Changed variable name `CURL_OPTS` to `CURL_OPTIONS` in the documentation block "Some noteworthy control variables" in `build.sh`. 
> 
> `CURL_OPTIONS` is used in the `download_using_curl()` function in `build-support/build-common.sh`.

Oleksii Sylichenko has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Update the second year of make/build.sh to 2025

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Changes:
  - all: https://git.openjdk.org/jtreg/pull/238/files
  - new: https://git.openjdk.org/jtreg/pull/238/files/14692275..a1c638f9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=238&range=02
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=238&range=01-02

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jtreg/pull/238.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/238/head:pull/238

PR: https://git.openjdk.org/jtreg/pull/238