Build a minimized Nix with MinGW

At this point many features are stripped out, but this works:

- Can run libnix{util,store,expr} unit tests
- Can run some Nix commands

Co-Authored-By volth <volth@volth.com>
Co-Authored-By Brian McKenna <brian@brianmckenna.org>

src/libstore/ca-specific-schema.sql

@@ -1,41 +0,0 @@
--- Extension of the sql schema for content-addressed derivations.
--- Won't be loaded unless the experimental feature `ca-derivations`
--- is enabled
-
-create table if not exists Realisations (
-    id integer primary key autoincrement not null,
-    drvPath text not null,
-    outputName text not null, -- symbolic output id, usually "out"
-    outputPath integer not null,
-    signatures text, -- space-separated list
-    foreign key (outputPath) references ValidPaths(id) on delete cascade
-);
-
-create index if not exists IndexRealisations on Realisations(drvPath, outputName);
-
--- We can end-up in a weird edge-case where a path depends on itself because
--- it’s an output of a CA derivation, that happens to be the same as one of its
--- dependencies.
--- In that case we have a dependency loop (path -> realisation1 -> realisation2
--- -> path) that we need to break by removing the dependencies between the
--- realisations
-create trigger if not exists DeleteSelfRefsViaRealisations before delete on ValidPaths
-  begin
-    delete from RealisationsRefs where realisationReference in (
-      select id from Realisations where outputPath = old.id
-    );
-  end;
-
-create table if not exists RealisationsRefs (
-    referrer integer not null,
-    realisationReference integer,
-    foreign key (referrer) references Realisations(id) on delete cascade,
-    foreign key (realisationReference) references Realisations(id) on delete restrict
-);
--- used by deletion trigger
-create index if not exists IndexRealisationsRefsRealisationReference on RealisationsRefs(realisationReference);
-
--- used by QueryRealisationReferences
-create index if not exists IndexRealisationsRefs on RealisationsRefs(referrer);
--- used by cascade deletion when ValidPaths is deleted
-create index if not exists IndexRealisationsRefsOnOutputPath on Realisations(outputPath);