Mbed_CLI search path for #include, how to mange this?

I’m new to Mbed_CLI. I’ve installed in in Ubuntu and also the GCC+ARM compiler.

I’m testing with a Blink example but this one uses ROS_Serial.

While compiling mbed-os I get the following error

./mbed-os/features/cellular/framework/AT/AT_CellularSMS.cpp:1134:38: error: ‘difftime’ was not declared in this scope
double diff = difftime(t1, t2);

I can’t see how this happens as AT_CellularSMS.cpp does include time.h as it should. If there were a bug in AT_CellularSMS.cpp others would notice.

I suspect some kind of problem with how *.h files are searched and some other time.h file is found.

How does one manage the search path for #include files?