main.cpp: unused-but-set-variable warnings for command line options with CONFIG+=serveronly

[hoffie]

Describe the bug

When building with CONFIG+=serveronly, gcc 10.2.1 emits the following warnings:

src/main.cpp: In function 'int main(int, char**)':
src/main.cpp:83:18: warning: variable 'bShowComplRegConnList' set but not used [-Wunused-but-set-variable]
   83 |     bool         bShowComplRegConnList       = false;
      |                  ^~~~~~~~~~~~~~~~~~~~~
src/main.cpp:87:18: warning: variable 'bShowAnalyzerConsole' set but not used [-Wunused-but-set-variable]
   87 |     bool         bShowAnalyzerConsole        = false;
      |                  ^~~~~~~~~~~~~~~~~~~~
src/main.cpp:88:18: warning: variable 'bMuteStream' set but not used [-Wunused-but-set-variable]
   88 |     bool         bMuteStream                 = false;
      |                  ^~~~~~~~~~~
src/main.cpp:92:18: warning: variable 'bNoAutoJackConnect' set but not used [-Wunused-but-set-variable]
   92 |     bool         bNoAutoJackConnect          = false;
      |                  ^~~~~~~~~~~~~~~~~~

To Reproduce

qmake CONFIG+=serveronly && make

Expected behavior

No warnings.

1. Those variables should either be used in the sense that we output an error/warning to the user if they are enabled despite not having an effect.
2. Alternatively, support for those flags and variables could be #ifdef'd out.
3. We could silence the warnings via Q_UNUSED(). I don't think we should do that.

Screenshots

Operating system

Debian 11

Version of Jamulus

master (a9deb22)