perl: fix configure step

Configure -A symbol=val generates a extra space in config.sh,
which causes failure like this :
    Building Module-Runtime-0.013
    Unknown OS type ' linux' - using default settings

[Arnout: use -A define:foo instead of patching config.sh]

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>