GHC requires itself to build, and unfortunately the only way to get a
working GHC for a foreign target is to do a cross-compilation.

In order to build a bootkit for a new platform, you need to manually
set up a cross-building C compiler and binutils, libc, libterminfo,
and libiconv for the target. Then you can follow instructions in
https://gitlab.haskell.org/ghc/ghc/wikis/building/cross-compiling

Once you get a working GHC for the target platform, install it
somewhere in your PATH, run "cd lang/ghc80; make clean; make bootstrap"
on the target platform and you'll have a bootkit for the target.

--

GHC in fact has never supported bootstrapping only with a C compiler.
Prior to GHC 7, it had a thing called "HC source", which was a set of
C source files compiled from Haskell source, but it wasn't actually
cross-platform. It was because HC files were generated with many
assumptions about the platform, such as the layout of libc structs,
the size of off_t and time_t, byte-order, word size, etc.