[PATCH] build: disable fcf-protection on -march=486 -m16

[christian . ehrhardt]

From: Christian Ehrhardt <christian.ehrhardt@canonical.com>

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>
---
 pc-bios/optionrom/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
index 5d55d25acc..f1ef898073 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
 
-- 
2.35.1