RFR: 8326412: debuginfo files should not have executable bit set

[Magnus Ihse Bursie]

When we create our debuginfo files on linux, we use objcopy to create a copy of the corresponding lib*.so or executable. In the latter case, objcopy will keep the executable bit. While this is a reasonable assumption for objcopy, we really treat the debuginfo files as data, not as executables in their own right, so we should strip the executable bit.

This was found when working with [JDK-8325342](https://bugs.openjdk.org/browse/JDK-8325342), and I there attempted to properly locate all executables and only executables.

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Commit messages:
 - 8326412: debuginfo files should not have executable bit set

Changes: https://git.openjdk.org/jdk/pull/17947/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17947&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326412
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17947.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17947/head:pull/17947

PR: https://git.openjdk.org/jdk/pull/17947