Fix IsUbuntu logic in build module
Fix IsUbuntu logic in build module

I previously broke the automatic uninstallation logic by changing how I
identified the Linux distribution.

kmosher/PowerShell,kmosher/PowerShell,JamesWTruher/PowerShell-1,bingbing8/PowerShell,PaulHigin/PowerShell,TravisEz13/PowerShell,daxian-dbw/PowerShell,kmosher/PowerShell,daxian-dbw/PowerShell,daxian-dbw/PowerShell,JamesWTruher/PowerShell-1,jsoref/PowerShell,jsoref/PowerShell,KarolKaczmarek/PowerShell,jsoref/PowerShell,bingbing8/PowerShell,bmanikm/PowerShell,bingbing8/PowerShell,TravisEz13/PowerShell,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,bingbing8/PowerShell,PaulHigin/PowerShell,kmosher/PowerShell,PaulHigin/PowerShell,bingbing8/PowerShell,TravisEz13/PowerShell,KarolKaczmarek/PowerShell,PaulHigin/PowerShell,KarolKaczmarek/PowerShell,jsoref/PowerShell,KarolKaczmarek/PowerShell,bmanikm/PowerShell,JamesWTruher/PowerShell-1,bmanikm/PowerShell,bmanikm/PowerShell,bmanikm/PowerShell,jsoref/PowerShell,KarolKaczmarek/PowerShell,kmosher/PowerShell,daxian-dbw/PowerShell