[php-src] Issue #24695: sapi/fpm/tests/tester.inc can send SIGUSR2 to pid 0, killing run-tests.php

Issue: https://github.com/php/php-src/issues/24695 Author: Bill-Sommerfeld ### Description While testing https://github.com/OpenIndiana/oi-userland/pull/28065, https://github.com/OpenIndiana/oi-userland/pull/28066, and https://github.com/OpenIndiana/oi-userland/pull/28067, (packaging 8.3.36, 8.4.27, and 8.5.12, respectively), I observed test runs aborting with a "User Signal 2" or "zsh: user-defined signal 2" error (the exact error depends on which shell you're running). Digging further I caught the test sapi/fpm/tests/bug80024-socket-reduced-inherit.phpt invoking kill -USR2 0; this sends a SIGUSR2 signal to the current process group, killing both the test and the run-tests.php test runner, aborting the test run. I worked around this with the attached "no-kill-zero.patch" which declines to send a signal if it can't find a non-zero pid. With this patch in place, run-tests.php can run to completion on openindiana. [no-kill-zero.patch](https://github.com/user-attachments/files/33930170/no-kill-zero.patch) Example of a run clobbered by this (without the patch): ``` builder@builder:/z/ws/oi-userland-dev/components/web/php/php-8_5$ gmake test COMPONENT_TEST_ARGS="TESTS=sapi/fpm/tests/bug80024-socket-reduced-inherit.phpt" /bin/rm -f -r /z/ws/oi-userland-dev/components/web/php/php-8_5/build/test/amd64 /bin/mkdir -p /z/ws/oi-userland-dev/components/web/php/php-8_5/build/test/amd64 (cd /z/ws/oi-userland-dev/components/web/php/php-8_5/build/amd64 ; \ /usr/bin/env -i CARGO_HOME="/z/ws/oi-userland-dev/components/web/php/php-8_5/build/amd64/.cargo" PATH="/usr/gcc/14/bin:/usr/clang/21/bin:/usr/ruby/3.2/bin:/usr/jdk/openjdk21/bin:/usr/postgres/16/bin:/usr/mariadb/10.6/bin:/usr/openssl/3/bin:/usr/bin/amd64:/usr/bin:/usr/gnu/bin:/usr/sbin/amd64:/usr/sbin" NO_INTERACTION=yes \ /usr/gnu/bin/make \ TESTS=sapi/fpm/tests/bug80024-socket-reduced-inherit.phpt test) \ |& /usr/bin/tee /z/ws/oi-userland-dev/components/web/php/php-8_5/build/test/amd64/test-64-results Build complete. Don't forget to run 'make test'. ===================================================================== PHP : /z/ws/oi-userland-dev/components/web/php/php-8_5/build/amd64/sapi/cli/php PHP_SAPI : cli PHP_VERSION : 8.5.12 ZEND_VERSION: 4.5.12 PHP_OS : SunOS - SunOS builder 5.11 illumos-de1199e407 i86pc INI actual : /z/ws/oi-userland-dev/components/web/php/php-8_5/build/amd64/tmp-php.ini More .INIs : --------------------------------------------------------------------- PHP : /z/ws/oi-userland-dev/components/web/php/php-8_5/build/amd64/sapi/cgi/php-cgi PHP_SAPI : cgi-fcgi PHP_VERSION : 8.5.12 ZEND_VERSION: 4.5.12 PHP_OS : SunOS - SunOS builder 5.11 illumos-de1199e407 i86pc INI actual : /z/ws/oi-userland-dev/components/web/php/php-8_5/build/amd64/tmp-php.ini More .INIs : --------------------------------------------------------------------- --------------------------------------------------------------------- PHP : /z/ws/oi-userland-dev/components/web/php/php-8_5/build/amd64/sapi/phpdbg/phpdbg PHP_SAPI : phpdbg PHP_VERSION : 8.5.12 ZEND_VERSION: 4.5.12 PHP_OS : SunOS - SunOS builder 5.11 illumos-de1199e407 i86pc INI actual : /z/ws/oi-userland-dev/components/web/php/php-8_5/build/amd64/tmp-php.ini More .INIs : --------------------------------------------------------------------- CWD : /z/ws/oi-userland-dev/components/web/php/php-8_5/php-8.5.12 Extra dirs : VALGRIND : Not used ===================================================================== Running selected tests. User Signal 2 gmake test COMPONENT_TEST_ARGS="TESTS=sapi/fpm/tests/bug80024-socket-reduced-inherit.phpt" ``` Output for 8.3.x and 8.4.x is similar. ### PHP Version ```plain Observed while running make test after builds of 8.3.36, 8.4.27, and 8.5.12 on openindiana. ``` ### Operating System Openindiana