libcamera: v4l2_videodevice: Fix potential errno overwrite

The errno variable can potentially be overwritten by operator<<(). Store
it in a local variable before logging the error message.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>

src/libcamera/v4l2_videodevice.cpp

@@ -647,14 +647,17 @@ int V4L2VideoDevice::open()
  */
 int V4L2VideoDevice::open(SharedFD handle, enum v4l2_buf_type type)
 {
+	int ret;
+
 	UniqueFD newFd = handle.dup();
 	if (!newFd.isValid()) {
+		ret = -errno;
 		LOG(V4L2, Error) << "Failed to duplicate file handle: "
-				 << strerror(errno);
+				 << strerror(-ret);
-		return -errno;
+		return ret;
 	}
 
-	int ret = V4L2Device::setFd(std::move(newFd));
+	ret = V4L2Device::setFd(std::move(newFd));
 	if (ret < 0) {
 		LOG(V4L2, Error) << "Failed to set file handle: "
 				 << strerror(-ret);