First time build fails for microchip-sama5d27-som1-ek1/127

It seems that you still have some local changes, as I have tested a build with my proposed change and it worked just fine.

Maybe best to start from fresh, following,

and then adding

 PREFERRED_VERSION_u-boot-at91 = "v2018.07-at91+gitAUTOINC+1e7d2e5973"

to your local.conf before building.