install.js default to i686 on non x64 linux

[fg2it]

The install script default for non x64 linux is intel i686 :

if (process.platform === 'linux' && process.arch === 'x64') {
      downloadUrl += 'linux-x86_64.tar.bz2'
} else if (process.platform === 'linux') {
      downloadUrl += 'linux-i686.tar.bz2'
}

This should not be the case. process.arch should match a 32 bit platform before selecting this
This create nasty problems on arm hardware (e.g. raspberry).

A simple fix is simply to fail the install, a second one would be to build from src but I would prefere an official arm package (e.g. targeting raspberry :-) ) since building from src would probably take a long time on such hardware.