Arduino IDE won't start if installed under a path that contains ;

Using Arduino IDE Beta Build 61 and Arduino IDE 1.8.6 Hourly Build 2018/05/28 09:33 under Windows 10 64 bit

Install the Arduino IDE under a folder that contains `;`.
Start the Arduino IDE. It fails:
```
C:\foo;bar\arduino-PR-beta1.9-BUILD-61>arduino_debug
Error occurred during initialization of VM
Unable to load native library: C:\foo;bar\arduino-PR-beta1.9-BUILD-61\java\lib\ext;C:\WINDOWS\Sun\Java\lib\ext
```

Reproduce on Windows 10 with Arduino IDE Beta Build 61 or the Arduino IDE 1.8.6 hourly build, installed under a folder containing `;`, and start it with `arduino_debug`. Use the reported VM initialization error as the failure to investigate; done means the IDE starts from that path.

Written by the indexing model from the issue text.