RFR: 8293004: (fs) copy_file_range needs fallback handling for ENOSYS

[Florian Weimer]

Now that the userspace emulation is not leveraged anymore, it would be possible to issue the system call directly for all glibc versions, but it's probably best not to start using `copy_file_range` where it hasn't been used before (the el7 kernel has a strange backport, if I recall correctly).

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Commit messages:
 - 8293004: (fs) copy_file_range needs fallback handling for ENOSYS

Changes: https://git.openjdk.org/jdk/pull/10055/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10055&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293004
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10055.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10055/head:pull/10055

PR: https://git.openjdk.org/jdk/pull/10055