ld.so will return 1 for a static executable

In that case, we should not wrap the execution with ld.so. This fixes an issue
Haiyan had with some Physics applications. execve would fail with EIO because
`ld.so --verify ...` had a non-zero exit status. Before commit
501d932db5a1cb769ddfb4ce43c99a113f1e2f93, Parrot would report the failure but
still allow the execve to continue.