RFR: 8364312: debug agent should set FD_CLOEXEC flag rather than explicitly closing every open file [v2]

[Guanqiang Han]

> Create a new function that marks all file descriptors found in /proc/self/fd with the FD_CLOEXEC flag to ensure they are automatically closed upon execution of a new program via exec().

Guanqiang Han has updated the pull request incrementally with one additional commit since the last revision:

  Update exec_md.c
  
  correct an compilation error

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Changes:
  - all: https://git.openjdk.org/jdk/pull/26568/files
  - new: https://git.openjdk.org/jdk/pull/26568/files/54fd3fb3..2e94cb44

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26568&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26568&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26568.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26568/head:pull/26568

PR: https://git.openjdk.org/jdk/pull/26568