RFR: 8206890: jlink --endian XXX generates unusable image if endian-ness does not match architecture

[Jaikiran Pai]

Can I please get a review for this change which proposes to fix the issue reported in https://bugs.openjdk.org/browse/JDK-8206890?

The `jlink` command allows a `--endian` option to specify the byte order in the generated image. Before this change, when such a image was being launched, the code would assume the byte order in the image to be the native order of the host where the image is being launched. That would result in failure to launch java, as noted in the linked issue.

The commit in this PR, changes relevant places to not assume native order and instead determine the byte order by reading the magic bytes in the image file's header content.

A new jtreg test has been added which reproduces the issue and verifies the fix.

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Commit messages:
 - fix jcheck issue - convert tab to space
 - Alan's input - remove "final" and match the current code style
 - take into account SecurityManager checks
 - 8206890: jlink --endian XXX generates unusable image if endian-ness does not match architecture

Changes: https://git.openjdk.org/jdk/pull/11943/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11943&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8206890
  Stats: 260 lines in 5 files changed: 250 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/11943.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11943/head:pull/11943

PR: https://git.openjdk.org/jdk/pull/11943