Setup the environment for the libc build

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>
Add initial glibc build

Modularization is coming soon.

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>
Switch "${prefix}/${target}" to "${sysroot}"

aka: Make sysroot more obvious

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>