Revert "Merge pull request #642 from dylan-lang/sigfpe-changes"

This reverts commit 4d8998903db66ebe58cac0805accd47f28096607, reversing
changes made to 794580fd9a2162172064db783bf7efbce09c3910.
Revert "[env] Fix use of wrong binding for build script."

This reverts commit 0c3c53a40a4338befaba9f881caf9d6a39d5a151.
Revert "Merge pull request #638 from dylan-lang/target-platform-cleanups"

This reverts commit 6701e5250a1d0661acd2eedd0f77b2d5284a258e, reversing
changes made to 1fcc438218ed01f103d4141e72106fdd0130fc4d.