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/globals/scripts/zig-cc.sh

@@ -68,13 +68,13 @@ done
 
 RT_DIR="${SPC_COMPILER_RT_DIR:-}"
 if [[ $IS_LINK -eq 1 && $NEED_PROFILE_RT -eq 1 && -n "$RT_DIR" && -f "$RT_DIR/libclang_rt.profile.a" ]]; then
-    PARSED_ARGS+=("$RT_DIR/libclang_rt.profile.a" "-Wl,-u,__llvm_profile_runtime")
+    PARSED_ARGS+=("-x" "none" "$RT_DIR/libclang_rt.profile.a" "-Wl,-u,__llvm_profile_runtime")
 fi
 if [[ $IS_LINK -eq 1 && $NEED_CRT -eq 1 && -n "$RT_DIR" && -f "$RT_DIR/clang_rt.crtbegin.o" && -f "$RT_DIR/clang_rt.crtend.o" ]]; then
-    PARSED_ARGS+=("$RT_DIR/clang_rt.crtbegin.o" "$RT_DIR/clang_rt.crtend.o")
+    PARSED_ARGS+=("-x" "none" "$RT_DIR/clang_rt.crtbegin.o" "$RT_DIR/clang_rt.crtend.o")
 fi
 if [[ $IS_LINK -eq 1 && -n "$RT_DIR" && -f "$RT_DIR/libclang_rt.cpu_model.a" ]]; then
-    PARSED_ARGS+=("$RT_DIR/libclang_rt.cpu_model.a")
+    PARSED_ARGS+=("-x" "none" "$RT_DIR/libclang_rt.cpu_model.a")
 fi
 
 [[ -n "$SPC_TARGET" ]] && TARGET="-target $SPC_TARGET" || TARGET=""