These changes are necessary for me to use mit-scheme on i686 NixOS.
mit-scheme in the current state should be broken on x86_64 either and
these changes should fix, too. I however did not test this.
When the ghc-paths library is compiled, the paths of the
compiler it is compiled with are being hardcoded in the
library (and can then be queried from other applications
using the library).
But on Nix, packages are compiled with ghc-wrapper, and
subsequently possibly used with a special version of ghc
generated for a particular environment of packages. So
one version of ghc-paths may potentially end up being
used by lots of different instances of ghc. The hardcoding
approach fails.
As a work-around, we now patch ghc-paths so that it allows
setting the paths that can be queried via environment
variables. Specific GHC environments can then set these
environment variables in the wrapper shell script that
invokes GHC.
This should at least partially solve issue #213.
Replacing SBCL upstream tracking expression with a new version in a new
format.
Minuses: gave up on defining everything in Nix language (now update
expression is a series of actions to do when downloading fresh release,
it is actually interpreted by shell), now Nix expression contains
meaningful whitespace (the area to regenerate is determined by the
line with a specific comment and the closing brace on the otherwise
empty line).
Plusses: only one extra file which could even be moved out-of-tree if
desired, clean semantics for traversing multiple links (it is not found
in either Debian uscan or Gentoo euscan), the main expression is in one
file and is less different from usual style.
Any attempt to instantiate these expressions on an unsupported platform is
going to 'throw' an error. The call to 'assert' doesn't add any value to
that (and generates less readable error messages, too). Further details are
available at <https://github.com/NixOS/nix/issues/56>.
