Makefile: Potential fix for locale-dependent sed.

Potential fix for [InfoKOM 742464]:

| 742464 idag 10:32 /10 rader/ Stefan Wallström (frequent flyer)
| Mottagare: Henrik Grubbström <5062>
| Mottagare: Stefan Wallström (frequent flyer) <1959>
| Ärende: sed pike 7.9
| ------------------------------------------------------------
| Compiling modules/Math/transforms.c
| Linking Math
| ld: warning: -read_only_relocs cannot be used with x86_64
| Making module.pmod
| sed: RE error: illegal byte sequence
| make[4]: *** [module.pmod] Error 1
| make[3]: *** [all] Error 2
| make[2]: *** [Math] Error 1
| make[1]: *** [dynamic_module_objects] Error 1
| make: *** [module_objects] Error 2
| (742464) /Stefan Wallström (frequent flyer)/--------