[Pkg-haskell-maintainers] Bug#783987: ghc: ghci on arm64

[Edmund Grimley Evans]

I noticed that there were a couple of aarch64-related commits on Apr 20/21:

https://git.haskell.org/ghc.git/commit/0bbc2ac6dae9ce2838f23a75a6a989826c06f3f5
https://git.haskell.org/ghc.git/commit/1e8c9b81a819da8eb54405a029fc33a9f5220321

I wondered what would happen if I applied them on top of Debian's 7.8.4-3.

I was able to apply the second patch, modifying mk/config.mk.in, with
a small offset.

I wasn't able to apply the first patch, modifying aclocal.m4, so I
thought, sod it, it's just a big set of macros, I'll just copy the
aclocal.m4 from the commit into the build tree.

So in effect I modified these two files:

d9d4bef616d3e7dde976227c80baa9a4  aclocal.m4
9292ce20044d931dc0cb7d3447dc1511  mk/config.mk.in

I wasn't really expecting anything good to come out of such a
simple-minded change, but in fact the patched 7.8.4-3 successfully
built an arm64 deb, which includes a ghci, which appears to work, at
least to the extent of evaluating some simple expressions on the
command line.

(And the unpatched 7.8.4-3 failed for me as it did on the buildd, so
it's not just that my environment is different.)