RFR: JDK-8231594: Configure fails on some Linux systems

[Erik Joelsson]

In my recent change JDK-8206125, I introduced a bash conditional that 
checks if a string starts with ~. That check seems to fail on some Linux 
systems unless the ~ is quoted.

Bug: https://bugs.openjdk.java.net/browse/JDK-8231594
Webrev: http://cr.openjdk.java.net/~erikj/8231594/webrev.01

/Erik