fix(headers): sys/timerfd.h must compile in plain C (unblocks Wayland/glib)

cbindgen auto-generated the timerfd_* prototypes from the Rust signatures,
emitting a bare 'itimerspec' (not 'struct itimerspec') and a 'clockid_t'
parameter with no <time.h> in scope, so any C program that #includes
<sys/timerfd.h> failed to compile. That made meson's TFD_CLOEXEC feature probe
report NO and aborted the whole Wayland stack (libwayland) and glib. Exclude the
auto-generated prototypes (the hand-written, correct ones are emitted from the
trailer) and add <time.h> to the sys_includes.

src/header/sys_timerfd/cbindgen.toml

@@ -5,8 +5,8 @@
 # in relibc. It is required by Qt6 for QSocketNotifier and many other
 # C programs that use timer file descriptors.
 #
-# Includes the itimerspec from <time.h>.
-sys_includes = ["signal.h", "stdint.h", "stddef.h"]
+# Includes clockid_t and struct itimerspec from <time.h>.
+sys_includes = ["signal.h", "stdint.h", "time.h", "stddef.h"]
 include_guard = "_SYS_TIMERFD_H"
 trailer = """
 #ifndef TFD_CLOEXEC
@@ -36,3 +36,12 @@ cpp_compat = true
 
 [enum]
 prefix_with_name = true
+
+# Do NOT auto-generate C prototypes from the Rust fn signatures: cbindgen
+# renders them with a bare `itimerspec` (rather than `struct itimerspec`) and a
+# `clockid_t` parameter, neither of which resolves in a plain C99 include of this
+# header, which broke every consumer that probes it (e.g. libwayland's
+# TFD_CLOEXEC feature test, gating the whole Wayland stack). The hand-written,
+# correct prototypes are emitted from the `trailer` above instead.
+[export]
+exclude = ["timerfd_create", "timerfd_settime", "timerfd_gettime"]