Undefined reference to `ping_start'

[matthew-william-lock]

I am running the following build command

mos build --local --platform esp8266 --verbose --clean

with a build target as shown below

libs_version: 2.20.0
modules_version: 2.20.0
mongoose_os_version: 2.20.0

I make use of a modified version of a community created watchdog_timer which makes use of various functions including ping_start, ping_regist_recv, and ping_regist_sent from lwip/app/ping.h.

When building with mongoose_os_version: 2.15.0 the library builds just fine.

However when building for mongoose_os_version: 2.20.0 it produces the following type of error :

/opt/Espressif/xtensa-lx106-elf/lib/gcc/xtensa-lx106-elf/9.2.0/../../../../xtensa-lx106-elf/bin/ld: /.../build/objs/mgos_watchdog.c.o: in function `mgos_watchdog_init_net_timer':
/.../libs/connection_watchdog/src/mgos_watchdog.c:162: undefined reference to `ping_start'