package/qemu: fix host-qemu compilation with Ubuntu GCC 11

Fixes:
cc1: error: ‘-fcf-protection’ is not compatible with this target

The new Ubuntu GCC packages (e.g. Ubuntu 11.2.0-7ubuntu2, 11.2.0) turn
on ‘-fcf-protection’ globally, which causes a build failure in the x86
realmode code. Turn it off explicitly on compilers that understand this
option.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/qemu/0002-build-disable-fcf-protection-on-march-486-m16.patch

@@ -0,0 +1,50 @@
+From 9584d3d00a454f47b0341465142bcf0735d734ae Mon Sep 17 00:00:00 2001
+From: Christian Ehrhardt <christian.ehrhardt@canonical.com>
+Date: Wed, 23 Mar 2022 10:07:13 +0100
+Subject: [PATCH] build: disable fcf-protection on -march=486 -m16
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Some of the roms build with -march=i486 -m16 which is incompatible
+with -fcf-protection. That in turn is can be set by default, for
+example in Ubuntu [1].
+That causes:
+ cc1: error: ‘-fcf-protection’ is not compatible with this target
+
+This won't work on -march=i486 -m16 and no matter if set or not we can
+override it to "none" if the option is known to the compiler to be
+able to build reliably.
+
+Fixes: https://gitlab.com/qemu-project/qemu/-/issues/889
+
+[1]: https://wiki.ubuntu.com/ToolChain/CompilerFlags#A-fcf-protection
+
+Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
+Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
+Reviewed-by: Thomas Huth <thuth@redhat.com>
+Message-Id: <20220323090713.1002588-1-christian.ehrhardt@canonical.com>
+Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
+Signed-off-by: Dario Binacchi <dariobin@libero.it>
+---
+ pc-bios/optionrom/Makefile | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
+index 5d55d25acca2..f1ef89807355 100644
+--- a/pc-bios/optionrom/Makefile
++++ b/pc-bios/optionrom/Makefile
+@@ -14,6 +14,10 @@ cc-option = $(if $(shell $(CC) $1 -c -o /dev/null -xc /dev/null >/dev/null 2>&1
+ 
+ override CFLAGS += -march=i486 -Wall
+ 
++# If -fcf-protection is enabled in flags or compiler defaults that will
++# conflict with -march=i486
++override CFLAGS += $(call cc-option, -fcf-protection=none)
++
+ # Flags for dependency generation
+ override CPPFLAGS += -MMD -MP -MT $@ -MF $(@D)/$(*F).d
+ 
+-- 
+2.32.0
+