Add simple support for --arch and LDC.
Add simple support for --arch and LDC.

grogancolin/dub,schuetzm/dub,xentec/dub,Flamaros/dub,gedaiu/dub,Abscissa/dub-data-mod,alexeibs/dub,nazriel/dub,rjframe/dub,p0nce/dub,Geod24/dub,jelmansouri/dub,y12uc231/dub,D-Programming-Language/dub,Abscissa/dub,jeanbaptistelab/dub,dreamsxin/dub