I experienced this problem on Debian while installing the C++ plugins, but it may happen on other Linux distros. If "
unzip" is not installed on the computer, then installing the plugins will fail. I'm assuming WPILib is being extracted 
from a .zip internally. Perhaps a more specific error message could be generated by the installation process (instead of
 "cpp" and "tools" plugins failing to install). I couldn't find any log file for more specific information. Also, some 
troubleshooting information regarding this could be added to the end of https://wpilib.screenstepslive.com/s/4485/m/
13503/l/145002-installing-eclipse-c-java.