Support btrfs on root in installer advanced options

[kmatt]

Is your feature request related to a problem? Please describe.

#448 suggests that btrfs on root was to be supported in release 31030.

Using 31980 iso image, advanced option allows CLR_ROOT to be formatted as btrfs, but installer will only proceed with ext* or xfs.

Describe the solution you'd like

Install root on btrfs, mainly to support compression on space limited VMs.

[mdhorn]

@kmatt We do not allow BTRFS for the root file systems as the clr-boot-manager does not support that file system. Issue #448 was to remove BTRFS as an option for the root file system, not to enable it.

Until the clr-boot-manager can support the root file system being formatted btrfs, the installer can not allow it.

[jennydaman]

@mdhorn I believe clr-boot-manager now supports BTRFS

clearlinux/clr-boot-manager#238

[victorstewart]

@jennydaman can you confirm you tried this and it works? btrfs is now allowed for the root filesystem?

[jennydaman]

Sorry @victorstewart i am not using clear linux anymore.