Disable assert() by default

platformio.ini

@@ -36,7 +36,7 @@ extra_configs =
 # Remove '-fmax-errors=5' from build_flags below to see all.
 #
 [common]
-build_flags        = -g3 -D__MARLIN_FIRMWARE__ -fmerge-constants
+build_flags        = -g3 -D__MARLIN_FIRMWARE__ -DNDEBUG -fmerge-constants
                      -fmax-errors=5
 extra_scripts      =
   pre:buildroot/share/PlatformIO/scripts/common-dependencies.py