"from glob import glob" instead of "import glob"
rename args to BaseBuilder.runtemplate
set up 'exists' and 'glob' in runtemplate rather than getdefaults
TreeBuilder uses templates full of commands (like ramdisk.ltmpl) to
create the output tree and boot images. There are 4 arch-specific
templates, plus a bonus EFI template which can handle EFI image creation
for any arch that implements EFI.