cpu/x86/64bit: Fix building with -jx

config.h is a dependency so add it.

Change-Id: Iac87039dd43aa75d49766b9a239fbd841ca6850c
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68244
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/cpu/x86/64bit/Makefile.inc b/src/cpu/x86/64bit/Makefile.inc
index 1895498..48f56fc 100644
--- a/src/cpu/x86/64bit/Makefile.inc
+++ b/src/cpu/x86/64bit/Makefile.inc
@@ -7,7 +7,7 @@
 ramstage-y += mode_switch.S
 
 # Add --defsym=_start=0 to suppress a linker warning.
-$(objcbfs)/pt: $(dir)/pt.S
+$(objcbfs)/pt: $(dir)/pt.S $(obj)/config.h
 	$(CC_bootblock) $(CFLAGS_bootblock) $(CPPFLAGS_bootblock) -o $@.tmp $< -Wl,--section-start=.rodata=$(CONFIG_ARCH_X86_64_PGTBL_LOC),--defsym=_start=0
 	$(OBJCOPY_ramstage) -Obinary -j .rodata $@.tmp $@
 	rm $@.tmp