[jdk11u-ri] RFR: 8210283: Support git as an SCM alternative in the build

[Erik Joelsson]

Backport of Git support to 11.0.0.1. Patch applies cleanly after [JDK-8210008](https://bugs.openjdk.org/browse/JDK-8210008).

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Depends on: https://git.openjdk.org/jdk11u-ri/pull/3

Commit messages:
 - JDK-8210283

Changes: https://git.openjdk.org/jdk11u-ri/pull/4/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-ri&pr=4&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8210283
  Stats: 55 lines in 5 files changed: 36 ins; 0 del; 19 mod
  Patch: https://git.openjdk.org/jdk11u-ri/pull/4.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-ri pull/4/head:pull/4

PR: https://git.openjdk.org/jdk11u-ri/pull/4