message: make context darwin arm64: removes workaround and uses the label
  directly. LLVM support those since quite some years now.
diff: @@ -64,9 +64,7 @@ _make_fcontext:
  ; compute abs address of label finish
  ; 0x0c = 3 instructions * size (4) before label 'finish'
  - ; TODO: Numeric offset since llvm still does not support labels in ADR. Fix:
  - ; http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140407/212336.html
  - adr x1, 0x0c
  + adr x1, finish
  ; save address of finish as return-address for context-function
  ; will be entered after context-function returns (LR register)
  