[tlbuild] gregorio doesn't build

[Akira Kakuto]

Hi Ken,

> Building the current TL sources fails as follows:
>
> make[4]: *** No rule to make target 'gregorio-4_2_0.exe', needed by 
> 'all-am'.  Stop.

Sorry, I'm responsible for the incorrect import of the 4.2.0.
Karl will correct when he has time.

Thanks,
Akira