Suppress unnecessary GCC truncation warnings using compiler directives

[AarC10]

#190 - Stop GCC from complaining in general about truncation issues using GCC compiler directives. This means that older GCC compilers will not get a warning. Tested on zephyr's eabi-gcc compiler which is on version 12.2

Unsure on whether or not we should remove the ignored variable and void cast now.

[RobMeades]

Hi, thanks for this. It's a shame that the non-#pramga removal mechanism doesn't work for your version of GCC; we usually try to avoid #pragma's because of the tendency of some compilers to emit an unknown #pragma, warning but I've run your PR through the test system and it doesn't appear to cause that on any of the compilers we currently support.

You will see from the All checks have failed red thingy that there's an AStyle issue in common/at_client/src/u_at_client.c:

If you could maybe fix that and re-push then I'll take your change internally, apply it and push it back to master here?

EDIT:

Unsure on whether or not we should remove the ignored variable and void cast now.

I think leave those in as that's the preferred mechanism that we may be able to move to at some point in the future.

[RobMeades]

Oh, and when you re-push you could change Supress -> Suppress also.