Adds new package options:
* enableDocs
* enableHaddockProgram
to control whether to build Sphinx docs, and GHC haddocks and the
haddock program.
Unfortunately currently the building of the `haddock `program
and generating GHC docs are mixed into one option, see:
https://gitlab.haskell.org/ghc/ghc/-/issues/20077
Making Sphinx docs disableable, and disabling them by default
for Musl and cross builds, makes it much easier to provide these
builds without having to support Sphinx's enormous dependency
tree for those ways of building.
With sphinx 4, interpreting the conf.py fails due to a decode
error: https://gitlab.haskell.org/ghc/ghc/-/issues/19962
The fix is an one line change which we have to backport from GHC master.
Thus ghcHEAD is not affected by this problem.
9.2 and 8.10.6 will most likely have a fix for this.
TODO: Patch 8.8.4 and 9.0.1
useLdGold previously just checked for useLLVM which (currently) implies
`linker == "lld"`. However more accurate is to check the `linker` of the
`targetPlatform` as it actually tells us which bintools package we can
expect.
`linker == "bfd"` implies that we are using the `binutils` package, so
gold is available, so we can use it unless musl is the libc. `linker ==
"gold"` implies that gold is the default linker already and we should
absolutely use it.
GHC calls otool on darwin which is contained in the
stdenv.cc.bintools.bintools derivation and thus needs adding to the
runtime PATH of GHC. Since this is toolchain specific technically, we
check for cctools instead of darwin (although I don't know if GHC
or nixpkgs work on macOS without cctools).
This fixes usage of GHC in an environment where otool is not available
and more specifically in stdenvNoCC which is used by writers.writeHaskell.
Resolves#123228.
