Let's be a bit more conservative here and actually fdatasync() the
configurations we're generating.
I'm seeing an issue at the moment where syslinux isn't finding the
config sometimes, and while I don't think this is the issue, let's try
it.
There was an attempted optimization to only write if changed, but this
is broken - we always write the bootloader config into a new
directory.
In theory we should only be writing if it changed, but let's not do a
broken optimization.
Colin Walters