Remove -Wno-digraphs from clang

[peterbarker]

Summary

Removes this compiler option as clang doesn't know about it. Also make unknown compiler options fatal as they may actually be important...

Classification & Testing (check all that apply and add your own)

• Checked by a human programmer
• Non-functional change
• No-binary change
• Infrastructure change (e.g. unit tests, helper scripts)
• Automated test(s) verify changes (e.g. unit test, autotest)
• Tested manually, description below (e.g. SITL)
• Tested on hardware
• Logs attached
• Logs available on request

Board                    AP_Periph  antennatracker  blimp  bootloader  copter  heli  iofirmware  plane  rover  sub
CubeOrange-periph-heavy  *                                 *
Durandal                            *               *      *           *       *                 *      *      *
Hitec-Airspeed           *                                 *
KakuteH7-bdshot                     *               *      *           *       *                 *      *      *
MatekF405                           *               *      *           *       *                 *      *      *
MatekH7A3                           *               *      *           *       *                 *      *      *
Pixhawk1-1M-bdshot                  *               *                  *       *                 *      *      *
SITL_x86_64_linux_gnu               *               *                  *       *                 *      *      *
YJUAV_A6SE                          *               *      *           *       *                 *      *      *
f103-QiotekPeriph        *                                 *
f303-MatekGPS            *                                 *
f303-Universal           *                                 *
iomcu                                                                                *
mindpx-v2                           *               *      *           *       *                 *      *      *
revo-mini                           *               *      *           *       *                 *      *      *
skyviper-v2450                                                         *
speedybeef4                         *               *      *           *       *                 *      *      *

... no vast amounts of warnings now for clang

Description

This warning was coming out a lot on clang. Compiles but warns.

Make the warning non-clang only and make future "don't know about this warning" fatal on clang.

[Huibean]

Thanks Peter, this fix my mac build, but seems like it break the CI

[peterbarker]

Thanks Peter, this fix my mac build, but seems like it break the CI

Yeah - I've pushed up another pair of patches for that.

I wouldn't be surprised if Plane breaks next on QURT - people were not particularly thorough and fixed only the Copter build for spewing out the warnings for logical-operations vs bitwise-operations...

[peterbarker]

... and another pair of fixes for frame size warnings...

[peterbarker]

... and some more fixes for stack sizes and now one for -Wformat-truncation

[tridge]

better add a link to the manual for "#endof"

[tridge]

right polarity on this?

[peterbarker]

Can be merged once claude says it is good

.... and no compiler output (should add clang to size_compare_branches.py somehow?)