edk2/Makefile: Add -v for compiler errors in the output

[philipanda]

I find it no fun to try and fix the ways of my coreboot+EDK2 inexperienced self without any errors being printed from EDK2 during the build.

[miczyg1]

@philipanda you don't need to do that. Simply invoke make V=1 when building coreboot, and edk2 will not be compiled in quiet mode. Then you will see all compiler errors, if any.

[philipanda]

@philipanda you don't need to do that. Simply invoke make V=1 when building coreboot, and edk2 will not be compiled in quiet mode. Then you will see all compiler errors, if any.

Thanks, I've checked that make help does indeed list that possibility in one of the first lines of the output.
In that case I think exposing this option to build.sh would be better suited for the discussion in #776