forward-port feat/pgo fixes

Forward-port the genuinely-new fixes from feat/pgo (2026-06-09 .. 07-09)
into v3's reorganized layout:

- zig-cc.sh: prefix runtime-lib appends with `-x none` so the profile/crt/
  cpu_model archives don't poison the following files as `-x c` sources
- ZigToolchain: set ax_cv_have_func_attribute_ifunc=no under -flto
  (an ifunc in LTO bitcode crashes zig 0.16's lld during thin-link)
- php configure: add --with-sysconfdir option; strip build-time env vars
  from phpinfo's "Configure Command"
- ext-brotli / ext-zstd: switch to stable release/tag tarballs; brotli
  configures with --with-libbrotli
- ext-event: patch libevent http_connection.c to use a const peer address
  (both static and shared builds)
- ghrel downloader: prefer GitHub's /releases/latest (the semantically
  latest stable release) over publish-order iteration, so a newer-tagged
  prerelease (e.g. libevent 2.2.x-alpha) can't win over 2.1.x-stable

Commits already present in v3 were skipped: protobuf-latest + libaom
ENABLE_*=OFF (9398a667), the clang runtime -target flag (2adedc09), the
runtime-bits fail-hard half of 3823631a, and github prefer-stable's
prerelease skip (incl. the ghtar /releases/latest path, already in v3).

src/Package/Target/php.php

@@ -143,6 +143,7 @@ class php extends TargetPackage
         $package->addBuildOption('disable-opcache-jit', null, null, 'Disable opcache jit');
         $package->addBuildOption('with-config-file-path', null, InputOption::VALUE_REQUIRED, 'Set the path in which to look for php.ini', PHP_OS_FAMILY === 'Windows' ? null : '/usr/local/etc/php');
         $package->addBuildOption('with-config-file-scan-dir', null, InputOption::VALUE_REQUIRED, 'Set the directory to scan for .ini files after reading php.ini', PHP_OS_FAMILY === 'Windows' ? null : '/usr/local/etc/php/conf.d');
+        $package->addBuildOption('with-sysconfdir', null, InputOption::VALUE_REQUIRED, 'Set the sysconfdir (e.g. /etc/php-zts) used by configure (not available on Windows)');
         $package->addBuildOption('with-hardcoded-ini', 'I', InputOption::VALUE_IS_ARRAY | InputOption::VALUE_REQUIRED, 'Patch PHP source code, inject hardcoded INI');
         $package->addBuildOption('enable-zts', null, null, 'Enable thread safe support');
         $package->addBuildOption('no-smoke-test', null, InputOption::VALUE_OPTIONAL, 'Disable smoke test for specific SAPIs, or all if no value provided', false);