RFR: 8323671: DevKit build gcc libraries contain full paths to source location

[Andrew Leonard]

This PR adds --with-debug-prefix-map to the building of gcc in the DevKit make file to map the top OUTPUT_ROOT folder to a standard "devkit" path, thus ensuring DevKit builds are reproducible regardless of the folder the DevKit is built within.

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Commit messages:
 - 8323671: DevKit build gcc libraries contain full paths to source location

Changes: https://git.openjdk.org/jdk/pull/17400/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17400&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323671
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17400.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17400/head:pull/17400

PR: https://git.openjdk.org/jdk/pull/17400