[jdk25u] RFR: 8364611: (process) Child process SIGPIPE signal disposition should be default

[Thomas Stuefe]

Hi all,

Unclean (but trivially merged) backport. We need to address this since we've started seeing it at two customers now, and it makes sense to fix it at least in the upcoming newest LTS. 

The backport is unclean since "8210549: Runtime.exec: in closeDescriptors(), use FD_CLOEXEC instead of close()" is in the way, and @RogerRiggs and I agreed on not backporting that one (had been purposely delayed to miss the JDK25 train).


- Tested on JDK25u on Linux x64 (ran java/lang/ProcessBuilder jtreg tests), which includes the provided regression test
- GHAs are clean

This pull request contains a backport of commit [bdb1646a](https://github.com/openjdk/jdk/commit/bdb1646a1e39bae0535efe3f593e7fc0545e4114) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Thomas Stuefe on 11 Aug 2025 and was reviewed by Erik Joelsson and Roger Riggs.

Thanks!

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Commit messages:
 - Merge branch 'openjdk:master' into backport-tstuefe-bdb1646a-master
 - Backport bdb1646a1e39bae0535efe3f593e7fc0545e4114

Changes: https://git.openjdk.org/jdk25u/pull/86/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u&pr=86&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8364611
  Stats: 196 lines in 5 files changed: 195 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk25u/pull/86.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u.git pull/86/head:pull/86

PR: https://git.openjdk.org/jdk25u/pull/86