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).
