RFR: 8276927: [PPC64] Port shenandoahgc to linux on ppc64le [v2]

[Niklas Radomski]

> Port the Shenandoah garbage collector (JDK-8241457)[https://bugs.openjdk.java.net/browse/JDK-8241457] to linux on ppc64le.

Niklas Radomski has updated the pull request incrementally with one additional commit since the last revision:

  Remove debug clobber code

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6325/files
  - new: https://git.openjdk.java.net/jdk/pull/6325/files/1dec8885..c504b66d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6325&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6325&range=00-01

  Stats: 5 lines in 1 file changed: 0 ins; 5 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6325.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6325/head:pull/6325

PR: https://git.openjdk.java.net/jdk/pull/6325