windows: add GetProcessId function

ref:
https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-getprocessid

Document does not say anything about return value, but when I use 0 for HANDLE, GetProcessId
returns 0 with ERROR_INVALID_HANDLE from GetLastError().

Change-Id: Ib6782ccd5a4917e93ddbcf18c533921b12c67e3b
Reviewed-on: https://go-review.googlesource.com/c/sys/+/180924
Reviewed-by: Marc-Antoine Ruel <maruel@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

windows/syscall_windows.go

@@ -266,6 +266,7 @@ func NewCallbackCDecl(fn interface{}) uintptr {
 //sys	GetPriorityClass(process Handle) (ret uint32, err error) = kernel32.GetPriorityClass
 //sys	SetInformationJobObject(job Handle, JobObjectInformationClass uint32, JobObjectInformation uintptr, JobObjectInformationLength uint32) (ret int, err error)
 //sys	GenerateConsoleCtrlEvent(ctrlEvent uint32, processGroupID uint32) (err error)
+//sys	GetProcessId(process Handle) (id uint32, err error)
 
 // Volume Management Functions
 //sys	DefineDosDevice(flags uint32, deviceName *uint16, targetPath *uint16) (err error) = DefineDosDeviceW

windows/zsyscall_windows.go

@@ -205,6 +205,7 @@ var (
 	procGetPriorityClass                   = modkernel32.NewProc("GetPriorityClass")
 	procSetInformationJobObject            = modkernel32.NewProc("SetInformationJobObject")
 	procGenerateConsoleCtrlEvent           = modkernel32.NewProc("GenerateConsoleCtrlEvent")
+	procGetProcessId                       = modkernel32.NewProc("GetProcessId")
 	procDefineDosDeviceW                   = modkernel32.NewProc("DefineDosDeviceW")
 	procDeleteVolumeMountPointW            = modkernel32.NewProc("DeleteVolumeMountPointW")
 	procFindFirstVolumeW                   = modkernel32.NewProc("FindFirstVolumeW")
@@ -2209,6 +2210,19 @@ func GenerateConsoleCtrlEvent(ctrlEvent uint32, processGroupID uint32) (err erro
 	return
 }
 
+func GetProcessId(process Handle) (id uint32, err error) {
+	r0, _, e1 := syscall.Syscall(procGetProcessId.Addr(), 1, uintptr(process), 0, 0)
+	id = uint32(r0)
+	if id == 0 {
+		if e1 != 0 {
+			err = errnoErr(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
 func DefineDosDevice(flags uint32, deviceName *uint16, targetPath *uint16) (err error) {
 	r1, _, e1 := syscall.Syscall(procDefineDosDeviceW.Addr(), 3, uintptr(flags), uintptr(unsafe.Pointer(deviceName)), uintptr(unsafe.Pointer(targetPath)))
 	if r1 == 0 {