RFR: 8357425: (fs) SecureDirectoryStream setPermissions should use fchmodat [v2]

[Brian Burkhalter]

> Modify to use the `fchmodat(2)` system call to set permissions where possible to do so. This fixes the problem presented in the issue description.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8357425: Use int mode = UnixFileModeAttribute.toUnixMode(perms)

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25534/files
  - new: https://git.openjdk.org/jdk/pull/25534/files/58cb7c9f..66de3e52

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25534&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25534&range=00-01

  Stats: 6 lines in 1 file changed: 1 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/25534.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25534/head:pull/25534

PR: https://git.openjdk.org/jdk/pull/25534