Add --compiler flag to runtests.sh.
Add --compiler flag to runtests.sh.

diku-dk/futhark,HIPERFIT/futhark,ihc/futhark,diku-dk/futhark,diku-dk/futhark,HIPERFIT/futhark,mrakgr/futhark,mrakgr/futhark,diku-dk/futhark,diku-dk/futhark,HIPERFIT/futhark,mrakgr/futhark,ihc/futhark,CulpaBS/wbBach,ihc/futhark