It must have been before 0.29 since platform.h.in mentions it, but as far as I know, no available compilers (Hugs, NHC) can compile 0.29 (i.e. it was probably strictly self hosting). But now that you mention it, it would be good to systematically try all of these. HBC we’d need a Lazy ML compiler for. (maybe it’s easier to write one than modifying Hugs?)
#define HC_UNSPECIFIED 1
#define HC_GLASGOW_GHC 2
#define HC_USE_HC_FILES 3
#define HC_CHALMERS_HBC 4
#define HC_ROJEMO_NHC 5
#define HC_YALE_YHC 6
#define HC_HUGS 7
(I did email Lennart Augustsson a few months back, but I never heard back)