Add CPU_X86_64 to "make features" printout

Signed-off-by: falkTX <falktx@falktx.com>

Makefile.base.mk

@@ -665,6 +665,7 @@ features:
 	$(call print_available,CPU_I386)
 	$(call print_available,CPU_I386_OR_X86_64)
 	$(call print_available,CPU_RISCV64)
+	$(call print_available,CPU_X86_64)
 	@echo === Detected OS
 	$(call print_available,BSD)
 	$(call print_available,HAIKU)