Removed compile warnings on Linux

[MatejFranceskin]

Building QGC on Ubuntu 19.10 with gcc (Ubuntu 9.2.1-9ubuntu2) 9.2.1 20191008 produces lots of warnings. Some of these warnings were already disabled in builds for other platforms so I added them also to Linux build.

[stefandunca]

Is it hard to fix those warnings? We should fix warnings unless we have a good reason. Event then the warning guards should be localized on the part of the code that can't get a fix.

[stefandunca]

Matej: "They come from QT headers and mavlink headers I think"
The build error is unrelated to the code: cc1plus: out of memory allocating 67108864 bytes after a total of 140865536 bytes

[DonLakeFlyer]

@stefandunca There a number of these which come from mavlink headers. Those should be fixed in mavlink to get mavlink headers to compile clean. Can you create an issue against mavlink so this can be fixed? I'm fine with turning those off until mavlink gets fixed.

no-deprecated-copy What is causing this one?

[DonLakeFlyer]

FYI: I'll see if pulling a new eigen will get rid of all the crap from there.

[MatejFranceskin]

There are a lot of deprecated-copy warnings coming from QT headers:

/home/matej/Qt/5.12.6/gcc_64/include/QtCore/qvariant.h: In constructor ‘QVariant::QVariant(QVariant&&)’:
/home/matej/Qt/5.12.6/gcc_64/include/QtCore/qvariant.h:273:25: warning: implicitly-declared ‘QVariant::Private& QVariant::Private::operator=(const QVariant::Private&)’ is deprecated [-Wdeprecated-copy]
273 | { other.d = Private(); }
| ^
/home/matej/Qt/5.12.6/gcc_64/include/QtCore/qvariant.h:399:16: note: because ‘QVariant::Private’ has user-provided ‘QVariant::Private::Private(const QVariant::Private&)’
399 | inline Private(const Private &other) Q_DECL_NOTHROW
| ^~~~~~~