In order to be able to perform a cross-build, we need to use
the stage1 binaries during installation. Both ghc and ghc-pkg
are run during the install target and therefore must be able
to run on the build machine.
Gbp-Pq: Name use-stage1-binaries-for-install.patch
This patch enables a few native 64-bit integer instructions
on x32 which are available on this architecture despite using
32-bit pointers. These instructions are present on x86_64 but
not on x86 and ghc checks the size of (void *) to determine
that. This method fails on x32 since despite using 32-bit
pointers and hence sizeof(void *) == 4, it still uses the
full x86_64 instruction set and software-emulated variants
of the aforementioned 64-bit integer instructions are
therefore not present in the toolchain which will make ghc
fail to build on x32.
See: https://ghc.haskell.org/trac/ghc/ticket/11571
Jani writes: The D16 part was Debian/Ubuntu specific, IIRC we define hardfloat
in that particular variant (16 double registers) or we had a different naming
for some reason.