build: Migrate Linux '.tar.gz' package creation from CPack to linuxdeployqt (#1034)

Unified Linux package creation into single script 'setup/Linux/createPackages.sh' that uses 'linuxdeployqt' for both the '.tar.gz' and '.AppImage' package.

script/buildonly.sh

@@ -51,11 +51,6 @@ then
 		#echo "debug app"
 		cmake --build build/Debug --target Sourcetrail
 	fi
-elif [ "$1" = "package" ] || [ "$1" = "p" ]
-then
-		cmake --build build/Release --target package
-		mv build/Release/Sourcetrail*.tar.gz . #&& cp build/Release/Sourcetrail*.deb distr
-		echo "Packages copied into the root folder"
 elif [ "$1" = "all" ] || [ "$1" = "a" ]
 then
 	cmake --build build/Release --target all