MFC r336535: Hoist EFI_TARGET and SOURCE_DATE_EPOCH up into efi/Makefile.inc
MFC r326038,r326069,r326072: More stand simplification and fixesr326038: Move some more common stuff up to Makefile.inc.r326069: Fix gptzfsboot for cases with GELI.r326072: Unbreak riscv build in universe.