RFR: 7903299: Add '.gradle/' and 'build/' to file '.gitignore'

[Guoxiong Li]

Hi all,

The directories '.gradle' and 'build/' are autumaticall created when opening and building the plugin project. It is good to ignore them in the git repo.

Thanks for taking time to review.

Best Regards,
-- Guoxiong

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Commit messages:
 - CODETOOLS-7903299

Changes: https://git.openjdk.org/jtreg/pull/116/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=116&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903299
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jtreg/pull/116.diff
  Fetch: git fetch https://git.openjdk.org/jtreg pull/116/head:pull/116

PR: https://git.openjdk.org/jtreg/pull/116