Comment 56 for bug 1866870

Starting from the Disco build env that I had I changed the packages

Step #1 binutils:
Unpacking binutils-x86-64-linux-gnu (2.33-2ubuntu1.2) over (2.32-7ubuntu4) ...
Unpacking libbinutils:amd64 (2.33-2ubuntu1.2) over (2.32-7ubuntu4) ...
Unpacking binutils (2.33-2ubuntu1.2) over (2.32-7ubuntu4) ...
Unpacking binutils-common:amd64 (2.33-2ubuntu1.2) over (2.32-7ubuntu4) ...

=> Still working

Step #2 gcc:
Unpacking libubsan1:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libtsan0:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking gcc-9-base:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libstdc++6:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libquadmath0:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking liblsan0:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libitm1:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libgomp1:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libcc1-0:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libatomic1:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libasan5:amd64 (9.2.1-9ubuntu2) over (9.1.0-2ubuntu2~19.04) ...
Unpacking libgcc1:amd64 (1:9.2.1-9ubuntu2) over (1:9.1.0-2ubuntu2~19.04) ...
Unpacking libisl21:amd64 (0.21-2) ...
Unpacking cpp-9 (9.2.1-9ubuntu2) ...
Unpacking libgcc-9-dev:amd64 (9.2.1-9ubuntu2) ...
Unpacking gcc-9 (9.2.1-9ubuntu2) ...
Unpacking libstdc++-9-dev:amd64 (9.2.1-9ubuntu2) ...
Unpacking g++-9 (9.2.1-9ubuntu2) ...
Unpacking g++ (4:9.2.1-3.1ubuntu1) over (4:8.3.0-1ubuntu3) ...
Unpacking gcc (4:9.2.1-3.1ubuntu1) over (4:8.3.0-1ubuntu3) ...
Unpacking cpp (4:9.2.1-3.1ubuntu1) over (4:8.3.0-1ubuntu3) ...

=> now it is breaking

One thing that we have seen to cause breakage in other cases was the new default to enable:
  -fcf-protection

The code already carries quite a bunch of similar "no" rules:
COMMONCFLAGS += $(call cc-option,$(CC),-nopie,)
COMMONCFLAGS += $(call cc-option,$(CC),-fno-pie,)
COMMONCFLAGS += $(call cc-option,$(CC),-fno-stack-protector,)
COMMONCFLAGS += $(call cc-option,$(CC),-fno-stack-protector-all,)
COMMONCFLAGS += $(call cc-option,$(CC),-fstack-check=no,)
COMMONCFLAGS += $(call cc-option,$(CC),-Wno-address-of-packed-member,)

Lets add to that:
COMMONCFLAGS += $(call cc-option,$(CC),-fcf-protection=none,)

=> That made it work \o/ !