https://bugs.gentoo.org/970040

--- a/Make.rules
+++ b/Make.rules
@@ -25,7 +25,7 @@
 LDSCRIPT	= elf_$(ARCH)_efi.lds
 LIBS		+= -nostdlib -shared -Bsymbolic $(CRTOBJS) -L $(CRTPATH) -T $(LDSCRIPT)
 LOADLIBES	= -lefi -lgnuefi $(shell $(CC) $(ARCH3264) -print-libgcc-file-name)
-FORMAT		= --target=efi-app-$(ARCH)
+FORMAT		= --output-target=efi-app-$(ARCH)
 MYGUID		= 11111111-2222-3333-4444-123456789abc
 INSTALL		= install
 BINDIR		= $(DESTDIR)/usr/bin