arch/x86: Make sure bootblock gets buildtested

Now that the bootblock isn't added to cbfs anymore, on some targets it's
only conditionally build. One example would be Intel APL where it only
gets build when stitched into an IFWI. This is always done when
compiling for real targets but not by the CI builder. This adds a dummy
target to make sure the bootblock always gets buildtested.

Change-Id: I60601e01a2c370b5c21493b71d51f495bb42f41d
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64427
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
diff --git a/src/arch/x86/Makefile.inc b/src/arch/x86/Makefile.inc
index e5d52ef..02ee902 100644
--- a/src/arch/x86/Makefile.inc
+++ b/src/arch/x86/Makefile.inc
@@ -108,6 +108,8 @@
 	@printf "    CBFS       $(subst $(obj)/,,$(@))\n"
 	$(CBFSTOOL) $< add -f $(objcbfs)/bootblock.bin  -n bootblock -t bootblock $(TXTIBB) -b -$(call file-size,$(objcbfs)/bootblock.bin) \
 	$(cbfs-autogen-attributes) $(TS_OPTIONS) $(CBFSTOOL_ADD_CMD_OPTIONS)
+else # Make sure the bootblock gets build, if only for buildtesting
+$(call add_intermediate, gen_bootblock, $(objcbfs)/bootblock.bin)
 endif
 endif