Fix forgotten errno return in evdev C code

xdg/keypressdetector/evdev.c

@@ -1,10 +1,11 @@
+#include <errno.h>
 #include "evdev.h"
 
 
 int block_until_keypress(const char* keyboardPath) {
     int keyboardFd = open(keyboardPath, O_RDONLY);
     if (keyboardFd < 0) {
-        return keyboardFd;
+        return errno;
     }
 
     int eventSize = sizeof(struct input_event);
@@ -15,7 +16,7 @@ int block_until_keypress(const char* keyboardPath) {
     while(readEvents) {
         bytesRead = read(keyboardFd, events, eventSize * NUM_EVENTS);
         if (bytesRead < 0) {
-            return bytesRead;
+            return errno;
         }
 
         for(int i = 0; i < (bytesRead / eventSize); ++i) {

xdg/keypressdetector/evdev.go

@@ -20,7 +20,7 @@ func (Evdev) BlockUntilKeypress(devicePath string) error {
 	defer C.free(unsafe.Pointer(path))
 
 	ret := C.block_until_keypress(path)
-	if ret < 0 {
+	if ret != 0 {
 		return syscall.Errno(ret)
 	}