[LinuxBIOS] OLPC buildsystem cleanups

[Carl-Daniel U. Hailfinger]

Hi,

the attached patches change the OLPC build system to use relative payload paths instead of using a hardcoded file in /tmp which will sooner or later cause security problems. Additionally, a check for config file correctness has been added so you can't accidentially generate the wrong payload for a given LinuxBIOS config.
I forgot how to invert command return codes in makefiles, so it would be cool if somebody could replace the FIXME in the olpc patch with the inverted grep command of some lines later.

Please note: The buildrom patch can only be applied upstream after teh LinuxBIOS patch has been applied upstream (and the needed svn revision obviously also has to be updated).

Regards,
Carl-Daniel