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/build/drv-output-substitution-goal.cc

@@ -1,167 +0,0 @@
-#include "drv-output-substitution-goal.hh"
-#include "finally.hh"
-#include "worker.hh"
-#include "substitution-goal.hh"
-#include "callback.hh"
-
-namespace nix {
-
-DrvOutputSubstitutionGoal::DrvOutputSubstitutionGoal(
-    const DrvOutput & id,
-    Worker & worker,
-    RepairFlag repair,
-    std::optional<ContentAddress> ca)
-    : Goal(worker, DerivedPath::Opaque { StorePath::dummy })
-    , id(id)
-{
-    state = &DrvOutputSubstitutionGoal::init;
-    name = fmt("substitution of '%s'", id.to_string());
-    trace("created");
-}
-
-
-void DrvOutputSubstitutionGoal::init()
-{
-    trace("init");
-
-    /* If the derivation already exists, we’re done */
-    if (worker.store.queryRealisation(id)) {
-        amDone(ecSuccess);
-        return;
-    }
-
-    subs = settings.useSubstitutes ? getDefaultSubstituters() : std::list<ref<Store>>();
-    tryNext();
-}
-
-void DrvOutputSubstitutionGoal::tryNext()
-{
-    trace("trying next substituter");
-
-    if (subs.size() == 0) {
-        /* None left.  Terminate this goal and let someone else deal
-           with it. */
-        debug("derivation output '%s' is required, but there is no substituter that can provide it", id.to_string());
-
-        /* Hack: don't indicate failure if there were no substituters.
-           In that case the calling derivation should just do a
-           build. */
-        amDone(substituterFailed ? ecFailed : ecNoSubstituters);
-
-        if (substituterFailed) {
-            worker.failedSubstitutions++;
-            worker.updateProgress();
-        }
-
-        return;
-    }
-
-    sub = subs.front();
-    subs.pop_front();
-
-    // FIXME: Make async
-    // outputInfo = sub->queryRealisation(id);
-
-    /* The callback of the curl download below can outlive `this` (if
-       some other error occurs), so it must not touch `this`. So put
-       the shared state in a separate refcounted object. */
-    downloadState = std::make_shared<DownloadState>();
-    downloadState->outPipe.create();
-
-    sub->queryRealisation(
-        id,
-        { [downloadState(downloadState)](std::future<std::shared_ptr<const Realisation>> res) {
-            try {
-                Finally updateStats([&]() { downloadState->outPipe.writeSide.close(); });
-                downloadState->promise.set_value(res.get());
-            } catch (...) {
-                downloadState->promise.set_exception(std::current_exception());
-            }
-        } });
-
-    worker.childStarted(shared_from_this(), {downloadState->outPipe.readSide.get()}, true, false);
-
-    state = &DrvOutputSubstitutionGoal::realisationFetched;
-}
-
-void DrvOutputSubstitutionGoal::realisationFetched()
-{
-    worker.childTerminated(this);
-
-    try {
-        outputInfo = downloadState->promise.get_future().get();
-    } catch (std::exception & e) {
-        printError(e.what());
-        substituterFailed = true;
-    }
-
-    if (!outputInfo) {
-        return tryNext();
-    }
-
-    for (const auto & [depId, depPath] : outputInfo->dependentRealisations) {
-        if (depId != id) {
-            if (auto localOutputInfo = worker.store.queryRealisation(depId);
-                localOutputInfo && localOutputInfo->outPath != depPath) {
-                warn(
-                    "substituter '%s' has an incompatible realisation for '%s', ignoring.\n"
-                    "Local:  %s\n"
-                    "Remote: %s",
-                    sub->getUri(),
-                    depId.to_string(),
-                    worker.store.printStorePath(localOutputInfo->outPath),
-                    worker.store.printStorePath(depPath)
-                );
-                tryNext();
-                return;
-            }
-            addWaitee(worker.makeDrvOutputSubstitutionGoal(depId));
-        }
-    }
-
-    addWaitee(worker.makePathSubstitutionGoal(outputInfo->outPath));
-
-    if (waitees.empty()) outPathValid();
-    else state = &DrvOutputSubstitutionGoal::outPathValid;
-}
-
-void DrvOutputSubstitutionGoal::outPathValid()
-{
-    assert(outputInfo);
-    trace("output path substituted");
-
-    if (nrFailed > 0) {
-        debug("The output path of the derivation output '%s' could not be substituted", id.to_string());
-        amDone(nrNoSubstituters > 0 || nrIncompleteClosure > 0 ? ecIncompleteClosure : ecFailed);
-        return;
-    }
-
-    worker.store.registerDrvOutput(*outputInfo);
-    finished();
-}
-
-void DrvOutputSubstitutionGoal::finished()
-{
-    trace("finished");
-    amDone(ecSuccess);
-}
-
-std::string DrvOutputSubstitutionGoal::key()
-{
-    /* "a$" ensures substitution goals happen before derivation
-       goals. */
-    return "a$" + std::string(id.to_string());
-}
-
-void DrvOutputSubstitutionGoal::work()
-{
-    (this->*state)();
-}
-
-void DrvOutputSubstitutionGoal::handleEOF(int fd)
-{
-    if (fd == downloadState->outPipe.readSide.get()) worker.wakeUp(shared_from_this());
-}
-
-
-}