RFR: 8320942: Only set openjdk-target when cross compiling linux-aarch64

[Mikael Vidstedt]

When building linux-aarch64 at Oracle using jib, --openjdk-target=aarch64-linux-gnu is always specified regardless of if building natively or cross compiling (on linux-x64). Among other things this has the (harmless) effect of tricking configure into thinking that it's cross compiling even for native builds:

checking whether we are cross compiling... yes

The reason is that the target value (aarch64-linux-gnu) doesn't match what config.guess returns (aarch64-unknown-linux-gnu). An explicit target is only needed when cross compiling and should not be specified for native builds.

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Commit messages:
 - 8320942: Only set openjdk-target when cross compiling

Changes: https://git.openjdk.org/jdk/pull/16873/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16873&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320942
  Stats: 5 lines in 1 file changed: 2 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16873.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16873/head:pull/16873

PR: https://git.openjdk.org/jdk/pull/16873