roms/Makefile: replace the $(EDK2_EFIROM) target with "edk2-basetools"

We don't (can't) have a recipe for building just $(EDK2_EFIROM);
therefore, while we call the target $(EDK2_EFIROM), we actually build all
of the edk2 BaseTools. Rename the target to edk2-basetools, and update the
iPXE prerequisite accordingly. This will let other targets depend on
"edk2-basetools", where an $(EDK2_EFIROM) pre-requisite would be
misleading.

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>

roms/Makefile

@@ -102,7 +102,7 @@ pxe-rom-%: build-pxe-roms
 
 efirom: $(patsubst %,efi-rom-%,$(pxerom_variants))
 
-efi-rom-%: build-pxe-roms build-efi-roms $(EDK2_EFIROM)
+efi-rom-%: build-pxe-roms build-efi-roms edk2-basetools
 	$(EDK2_EFIROM) -f "0x$(VID)" -i "0x$(DID)" -l 0x02 \
 		-b ipxe/src/bin/$(VID)$(DID).rom \
 		-ec ipxe/src/bin-i386-efi/$(VID)$(DID).efidrv \
@@ -131,7 +131,7 @@ build-efi-roms: build-pxe-roms
 #    EDK2_BASETOOLS_LDFLAGS='...' \
 #    efirom
 #
-$(EDK2_EFIROM):
+edk2-basetools:
 	$(MAKE) -C edk2/BaseTools \
 		EXTRA_OPTFLAGS='$(EDK2_BASETOOLS_OPTFLAGS)' \
 		EXTRA_LDFLAGS='$(EDK2_BASETOOLS_LDFLAGS)'