[LyX/master] Avoid bogus warnings when configuring for Qt6

[Richard Kimberly Heck]

On 7/3/24 6:55 AM, Enrico Forestieri wrote:
> On Tue, Jun 18, 2024 at 09:29:58PM +0100, José Matos wrote:
>>
>> On Tue, 2024-06-18 at 20:04 +0000, Enrico Forestieri wrote:
>>>     Avoid bogus warnings when configuring for Qt6
>>
>> Thank you. It works. :-)
>
> Riki, Ok for stable?

Yes, thanks.

Riki