GHC 8.8.2 Bootstrap Build Fails on macOS Catalina 10.15, undeclared identifier 'TAG_MASK'

[Steven Smith]

I’m trying to upgrade the MacPorts ghc install to the latest 8.8.2.

The build fails with:
> error: use of undeclared identifier 'TAG_MASK'
> :info:build         return (StgWord)p & TAG_MASK;


This is an error observed with previous ghc versions and on other systems, so I do not believe it is macOS-specific.  Also, the MacPorts build process simply follows the ghc Build & Install instructions: https://github.com/ghc/ghc/blob/master/README.md#building--installing

Is there a simple fix by adding an extra flag somewhere?

Logs:

> :info:build In file included from compiler/ghci/keepCAFsForGHCi.c:1:0: error: 
> :info:build In file included from includes/Rts.h:191:0: error: 
> :info:build includes/rts/storage/ClosureMacros.h:211:25: error:
> :info:build      error: use of undeclared identifier 'TAG_MASK'
> :info:build         return (StgWord)p & TAG_MASK;
> :info:build                             ^
> :info:build     |
> :info:build 211 |     return (StgWord)p & TAG_MASK;
> :info:build     |                         ^
> :info:build includes/rts/storage/ClosureMacros.h:217:40: error:
> :info:build      error: use of undeclared identifier 'TAG_MASK'
> :info:build         return (StgClosure*)((StgWord)p & ~TAG_MASK);
> :info:build                                            ^
> :info:build     |
> :info:build 217 |     return (StgClosure*)((StgWord)p & ~TAG_MASK);
> :info:build     |                                        ^
> :info:build includes/rts/storage/ClosureMacros.h:223:46: error:
> :info:build      error: use of undeclared identifier 'TAG_MASK'
> :info:build         return (const StgClosure*)((StgWord)p & ~TAG_MASK);
> :info:build                                                  ^
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