[jdk11u-dev] RFR: 8218413: make reconfigure ignores configure-time AUTOCONF environment variable

[George Adams]

Backport applies cleanly and is a prerequisite of https://github.com/openjdk/jdk11u-dev/pull/1277

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Commit messages:
 - Backport 9efdb33a59f7db7b4b39e113265a3b3ba513c5d3

Changes: https://git.openjdk.org/jdk11u-dev/pull/1300/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1300&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8218413
  Stats: 8 lines in 3 files changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1300.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1300/head:pull/1300

PR: https://git.openjdk.org/jdk11u-dev/pull/1300