List bin/process_signal_map.h (series 0016). The port copies the header
itself from files/process_signal_map.h.
FreeBSD-specific, not submitted upstream yet.
--- runtime/bin/io_impl_sources.gni.orig	2026-09-29 08:00:52 UTC
+++ runtime/bin/io_impl_sources.gni
@@ -51,6 +51,7 @@ io_impl_sources = [
   "process_fuchsia.cc",
   "process_linux.cc",
   "process_macos.cc",
+  "process_signal_map.h",
   "process_win.cc",
   "reference_counting.h",
   "root_certificates_unsupported.cc",