bug#15991: 24.3.50; Wishlist: Make test suite user-friendlier

[Glenn Morris]

Eli Zaretskii wrote:

>> All I can suggest here is that the Makefile define a GDB variable,
>> normally empty, that you can set to "gdb" on the make command-line when
>> you want to.
>
> I guess it would be OK, if $GDB could be set to "gdb --args".  Thanks.

I added $GDB at what seems like the right place.

I think this issue is done now.