Return exit code in Linux unit tests
Return exit code in Linux unit tests

Fixes #2681

xtermjs/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,sourcelair/xterm.js,Tyriar/xterm.js,Tyriar/xterm.js,Tyriar/xterm.js,Tyriar/xterm.js,xtermjs/xterm.js