RFR: 7903765: wget failed in build.sh in jtreg

[Jaikiran Pai]

Can I get a review of this change which proposes to address the issue noted in https://bugs.openjdk.org/browse/CODETOOLS-7903765? This is an alternative approach that we decided to take when reviewing the original PR for this issue https://github.com/openjdk/jtreg/pull/211.

In this change, when passing destination directories for downloading source archives of asmtools and jtharness, we pass the absolute path instead of paths containing relative path elements (like `../`). This change prevents `wget` running into an issue when dealing with destination directories containing `../` path element.

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Commit messages:
 - don't pass relative destination directories to asmtools and jtharness downloads

Changes: https://git.openjdk.org/jtreg/pull/214/files
  Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=214&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903765
  Stats: 11 lines in 3 files changed: 3 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jtreg/pull/214.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/214/head:pull/214

PR: https://git.openjdk.org/jtreg/pull/214