native: ignore format-truncation warnings (REVERTME)

This is enabled by default in GCC 7, disable for now. Tracked in
issue zephyrproject-rtos#5732

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

arch/posix/CMakeLists.txt

@@ -1,6 +1,7 @@
 zephyr_cc_option_ifdef(CONFIG_LTO -flto)
 
 zephyr_compile_options(
+  -Wno-format-truncation
   -fno-freestanding
   -Wno-undef
   -Wno-implicit-function-declaration