RFR: 8309356: Read files in includedir in alphanumeric order

[Weijun Wang]

Read files in `includedir` in alphanumerical order.

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

Commit messages:
 - remove x bits
 - the fix

Changes: https://git.openjdk.org/jdk/pull/15889/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15889&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309356
  Stats: 77 lines in 2 files changed: 73 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15889.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15889/head:pull/15889

PR: https://git.openjdk.org/jdk/pull/15889