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/posix-fs-canonicalise.hh

@@ -1,45 +0,0 @@
-#pragma once
-///@file
-
-#include <sys/stat.h>
-#include <sys/time.h>
-
-#include "types.hh"
-#include "error.hh"
-
-namespace nix {
-
-typedef std::pair<dev_t, ino_t> Inode;
-typedef std::set<Inode> InodesSeen;
-
-
-/**
- * "Fix", or canonicalise, the meta-data of the files in a store path
- * after it has been built.  In particular:
- *
- * - the last modification date on each file is set to 1 (i.e.,
- *   00:00:01 1/1/1970 UTC)
- *
- * - the permissions are set of 444 or 555 (i.e., read-only with or
- *   without execute permission; setuid bits etc. are cleared)
- *
- * - the owner and group are set to the Nix user and group, if we're
- *   running as root.
- *
- * If uidRange is not empty, this function will throw an error if it
- * encounters files owned by a user outside of the closed interval
- * [uidRange->first, uidRange->second].
- */
-void canonicalisePathMetaData(
-    const Path & path,
-    std::optional<std::pair<uid_t, uid_t>> uidRange,
-    InodesSeen & inodesSeen);
-void canonicalisePathMetaData(
-    const Path & path,
-    std::optional<std::pair<uid_t, uid_t>> uidRange);
-
-void canonicaliseTimestampAndPermissions(const Path & path);
-
-MakeError(PathInUse, Error);
-
-}