Fix issues with building external projects.
Fix issues with building external projects.

The supplied external project was not built in some cases, where the
superbuild system thought the target is up-to-date. Issue a build "all"
in an additionally supplied directory instead.

rfloca/MITK,danielknorr/MITK,lsanzdiaz/MITK-BiiG,RabadanLab/MITKats,lsanzdiaz/MITK-BiiG,MITK/MITK,rfloca/MITK,RabadanLab/MITKats,rfloca/MITK,RabadanLab/MITKats,lsanzdiaz/MITK-BiiG,NifTK/MITK,nocnokneo/MITK,NifTK/MITK,fmilano/mitk,NifTK/MITK,NifTK/MITK,lsanzdiaz/MITK-BiiG,rfloca/MITK,fmilano/mitk,iwegner/MITK,fmilano/mitk,NifTK/MITK,rfloca/MITK,danielknorr/MITK,iwegner/MITK,iwegner/MITK,fmilano/mitk,nocnokneo/MITK,RabadanLab/MITKats,rfloca/MITK,MITK/MITK,nocnokneo/MITK,MITK/MITK,fmilano/mitk,danielknorr/MITK,iwegner/MITK,MITK/MITK,RabadanLab/MITKats,danielknorr/MITK,fmilano/mitk,nocnokneo/MITK,lsanzdiaz/MITK-BiiG,RabadanLab/MITKats,iwegner/MITK,fmilano/mitk,lsanzdiaz/MITK-BiiG,danielknorr/MITK,danielknorr/MITK,rfloca/MITK,danielknorr/MITK,nocnokneo/MITK,lsanzdiaz/MITK-BiiG,NifTK/MITK,MITK/MITK,MITK/MITK,iwegner/MITK,lsanzdiaz/MITK-BiiG,nocnokneo/MITK,nocnokneo/MITK