RFR: JDK-8261261: The version extra fields needs to be overridable in jib-profiles.js

[Erik Joelsson]

The Oracle internal file jib-profiles.js needs needs the getVersion function extended so that the extra1-3 fields can be overridden just like the existing version fields.

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Commit messages:
 - Make extra1-3 overridable

Changes: https://git.openjdk.java.net/jdk/pull/2435/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2435&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261261
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2435.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2435/head:pull/2435

PR: https://git.openjdk.java.net/jdk/pull/2435