RFR: 8323667: Library debug files contain non-reproducible full gcc include paths

[Andrew Leonard]

For gcc toolchains in ALLOW_ABSOLUTE_PATHS_IN_OUTPUT=False builds, this PR finds the location of the gcc system include paths, and adds -fdebug-prefix-map flags to map them to a standard location. Thus making the debuginfo and resulting libraries reproducible when using DevKits in different path locations.

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Commit messages:
 - 8323667: Library debug files contain non-reproducible full gcc include paths

Changes: https://git.openjdk.org/jdk/pull/17399/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17399&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323667
  Stats: 51 lines in 1 file changed: 51 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17399.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17399/head:pull/17399

PR: https://git.openjdk.org/jdk/pull/17399