RFR: 8301753: AppendFile needs to add a new line to be compatible with old make

[Leonid Mesnik]

The newline is added to be compatible with old make 3.81 which is still used on MacOSX.
Fixed actually by dnsimon.

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Commit messages:
 - 8301753: AppendFile needs to add a new line to be compatible with old make

Changes: https://git.openjdk.org/jdk/pull/12461/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12461&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301753
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12461.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12461/head:pull/12461

PR: https://git.openjdk.org/jdk/pull/12461