Inject -Wno-error=format-overflow -Wno-error=format-truncation in debian/rules

In contrary to Debian, we use by default -Wformat-overflow=2
and -Wformat-truncation=2 in Apertis, but due to the use of -Werror this
package FTBFS with: "cc1: all warnings being treated as errors".
In order to avoid this error, we don't treat these warnings as errors.

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>

debian/rules

@@ -8,6 +8,13 @@ export LC_ALL = C.UTF-8
 include /usr/share/dpkg/default.mk
 include /usr/share/debhelper/dh_package_notes/package-notes.mk
 
+# In contrary to Debian, we use by default -Wformat-overflow=2 -Wformat-truncation=2
+# in Apertis, but due to the use of -Werror this package FTBFS with:
+# "cc1: all warnings being treated as errors". In order to avoid this error, we
+# don't treat these warnings as errors.
+export DEB_CFLAGS_MAINT_APPEND += -Wno-error=format-overflow -Wno-error=format-truncation
+export DEB_CXXFLAGS_MAINT_APPEND += -Wno-error=format-overflow -Wno-error=format-truncation
+
 ifeq (amd64,$(DEB_HOST_ARCH))
 export TEMPLATE_EFI_ARCH=x64
 else ifeq (arm64,$(DEB_HOST_ARCH))