[mlton/f19] (4 commits) ...Try a more generalized bootstrap approach

[Adam Goode]

Summary of changes:

  b24e158... Bootstrap ppc64 (*)
  c166752... Fix ppc64 bootstrap (*)
  a54bcbd... Really fix builds by more intelligently setting max-heap (*)
  54e2204... Try a more generalized bootstrap approach (*)

(*) This commit already existed in another branch; no separate mail sent