Only check that built implementation still exists
Only check that built implementation still exists

Testing that we can solve for it may fail if, for example, it is a library (and
so can't be run).

0install/0compile,0install/0compile,gfxmonk/0compile,dabrahams/0compile,timbertson/0compile,timbertson/0compile,0install/0compile,gfxmonk/0compile,dabrahams/0compile