I don't think putting up km2 of solar in the Sahara will solve the problem. You just can't ship electricity that far. We're at the point where we need to build any and all green power supplies as much and as quickly as possible if we want to get past this.
While it certainly possible to ship electricity over such distances (there are connections from e.g. Norway to the UK or Europe) I agree that that should not be the priority. There is huge potential for renewables within Europe first. Most places in southern Europe still have very little solar (AFAIK Germany has by quite a margin the most Solar installations in Europe and it definitely is not the best geographically). Sweden has huge potential for wind but hardly any installationsjust two name two things.
Another aspect that should not be ignored are the efficiency gains of producing electricity close to where it is used by e.g. roof top solar
