Seems to be some kind of confusion in gcc. Insteading of playing whack-a-mole and
adding work-arounds in code, let's adjust the compilation options instead.
Fixes #6119, replaces #6657.
foreach arg : ['unused-parameter',
'missing-field-initializers',
'unused-result',
- 'format-signedness']
+ 'format-signedness',
+ 'error=nonnull', # work-around for gcc 7.1 turning this on on its own
+ ]
if cc.has_argument('-W' + arg)
add_project_arguments('-Wno-' + arg, language : 'c')
endif