headers: fail Build on missing native exports and assert MI/COM layouts (#2739)

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

internal/headers/ntdll/ntdll.go

@@ -18,6 +18,7 @@
 package ntdll
 
 import (
+	"github.com/prometheus-community/windows_exporter/internal/headers/lazyproc"
 	"golang.org/x/sys/windows"
 )
 
@@ -25,8 +26,14 @@ import (
 var (
 	modNtdll                  = windows.NewLazySystemDLL("ntdll.dll")
 	procRtlNtStatusToDosError = modNtdll.NewProc("RtlNtStatusToDosError")
+
+	load = lazyproc.Once(modNtdll, procRtlNtStatusToDosError)
 )
 
+// Load checks that ntdll.dll exports every function of this package. Call it
+// in Build: a missing export panics on the first call otherwise.
+func Load() error { return load() }
+
 func RtlNtStatusToDosError(status uintptr) error {
 	ret, _, _ := procRtlNtStatusToDosError.Call(status)
 	if ret == 0 {