[syslinux] [PATCH] check-gnu-efi.sh: print the output of build-gnu-efi.sh

[Ady]

> _ The gnu-efi git repository is currently partially unavailable. Trying 
> to retrieve older commits (as the one used in the official release of 
> Syslinux 6.03 stable) might succeed, but, at this moment, trying to 
> retrieve the official gnu-efi master head will fail.
 
Update: after several days, the gnu-efi master head is now available 
again.

I do not discard the possibility of seeing it disappearing again in the 
future, as this seems to be a misunderstanding / mismanagement of the 
git repo / git commands.

Regards,
Ady.