haskell.compiler.*: pass runtime dependencies via configure script

GHC can actually accept absolute paths for its runtime tools (except for
touch) at configure time which are then saved in
`$out/lib/ghc-${version}/settings`. This allows us to drop the wrapper
entirely if we assume that a POSIX compliant touch is in PATH when we
run GHC later.

The touch problem can presumably be fixed by either patching the
configure file of GHC (although we need to take care not to change the
touch GHC uses during its compilation) or messing with the settings file
after installation.

The rationale for dropping the wrapper PATH entry completely is that
it's always possible to invoke GHC via its library which will bypass the
wrapper completely, leading to subtly different behavior.

Binary GHCs are not touched in this commit, but ideally they'll get a
similar treatment as well, so they are more robust, although we
generally don't need to use them as a library.

Note that GHC 8.8.4 doesn't care about install_name_tool or otool, so
the respective environment variables are not set.

0 files changed, 0 insertions, 0 deletions