Clean up build warnings (#4169)

* [build][OSX] Fix clang warnings.

* [build][OSX] A few more warnings taken care of.

* [build] Fixed yet more build warnings across all platforms.

* [build] Fix final warning due to bad CMake flag.

* [build] Remove unused variables as requested, fix indent.

* Fix output display limit type for 8-bit targets.

companion/src/logsdialog.cpp

@@ -507,7 +507,7 @@ QString LogsDialog::formatTimeDelta(double timeDelta)
     return QString("%1 s").arg(timeDelta, 1, 'f', 1);
   }
 
-  int seconds = (int)round(abs(timeDelta));
+  int seconds = (int)round(fabs(timeDelta));
   int hours = seconds / 3600;
   seconds %= 3600;
   int minutes = seconds / 60;