Create no-op Window pathlocks implementation

This keeps the call sites simple, eventually this should be filled in.

src/libstore/pathlocks.hh

@@ -5,22 +5,6 @@
 
 namespace nix {
 
-/**
- * Open (possibly create) a lock file and return the file descriptor.
- * -1 is returned if create is false and the lock could not be opened
- * because it doesn't exist.  Any other error throws an exception.
- */
-AutoCloseFD openLockFile(const Path & path, bool create);
-
-/**
- * Delete an open lock file.
- */
-void deleteLockFile(const Path & path, int fd);
-
-enum LockType { ltRead, ltWrite, ltNone };
-
-bool lockFile(int fd, LockType lockType, bool wait);
-
 class PathLocks
 {
 private:
@@ -40,18 +24,6 @@ public:
     void setDeletion(bool deletePaths);
 };
 
-struct FdLock
-{
-    int fd;
-    bool acquired = false;
-
-    FdLock(int fd, LockType lockType, bool wait, std::string_view waitMsg);
-
-    ~FdLock()
-    {
-        if (acquired)
-            lockFile(fd, ltNone, false);
-    }
-};
-
 }
+
+#include "pathlocks-impl.hh"