emulation/qemu-x86: Use common romstage code

This provides stack guards with checking and common
entry into postcar.

Change-Id: If0729721f0165187946107eb98e8bc754f28e517
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34973
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/cpu/qemu-x86/Makefile.inc

@@ -14,7 +14,11 @@
 
 bootblock-y += cache_as_ram_bootblock.S
 bootblock-y += bootblock.c
+
+romstage-y += ../intel/car/romstage.c
+
 ramstage-y += qemu.c
+
 subdirs-y += ../x86/mtrr
 subdirs-y += ../x86/lapic
 subdirs-y += ../x86/smm