ghc: build failure: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]

[i0ntempest]

:info:build | Run GhcPkg Update Stage1: _build/stage1/libraries/ghc-boot-th/inplace-pkg-config => none
:info:build In file included from rts/linker/SymbolExtras.c:12:0: error: 
:info:build In file included from rts/LinkerInternals.h:11:0: error: 
:info:build In file included from rts/include/Rts.h:38:0: error: 
:info:build In file included from rts/include/Stg.h:415:0: error: 
:info:build rts/include/stg/SMP.h:593:38: error:
:info:build      warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
:info:build     |
:info:build 593 | EXTERN_INLINE void write_barrier     () {} /* nothing */
:info:build     |                                      ^
:info:build EXTERN_INLINE void write_barrier     () {} /* nothing */
:info:build                                      ^
:info:build                                       void
:info:build rts/include/stg/SMP.h:594:38: error:
:info:build      warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
:info:build     |
:info:build 594 | EXTERN_INLINE void store_load_barrier() {} /* nothing */
:info:build     |                                      ^
:info:build EXTERN_INLINE void store_load_barrier() {} /* nothing */
:info:build                                      ^
:info:build                                       void
:info:build rts/include/stg/SMP.h:595:38: error:
:info:build      warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
:info:build     |
:info:build 595 | EXTERN_INLINE void load_load_barrier () {} /* nothing */
:info:build     |                                      ^
:info:build EXTERN_INLINE void load_load_barrier () {} /* nothing */
:info:build                                      ^
:info:build                                       void
:info:build 3 warnings generated.

Looks like this should be just a warning, but ghc build process treated it as an error.