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

@@ -18,6 +18,13 @@ DEB_LDFLAGS_MAINT_APPEND += -Wl,-O1
 
 include /usr/share/dpkg/default.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
+
 %:
 	dh $@