Re-enable util_datadir check disabled in #20744

This should also fix an assert error if a -datadir with a trailing slash
is used on windows. This appears to be a real error and regression
introduced with #20744.

On windows (or at least wine), fs calls that actuallly access the
filesystem like fs::equivalent or fs::exists seem to treat directory
paths with trailing slashes as not existing, so it's necessary to
normalize these paths before using them. This fix adds a
path::lexically_normal() call to the failing assert so it passes.

src/test/util_tests.cpp

@@ -71,12 +71,9 @@ BOOST_AUTO_TEST_CASE(util_datadir)
     args.ClearPathCache();
     BOOST_CHECK_EQUAL(dd_norm, args.GetDataDirBase());
 
-#ifndef WIN32
-    // Windows does not consider "datadir/.//" to be a valid directory path.
     args.ForceSetArg("-datadir", fs::PathToString(dd_norm) + "/.//");
     args.ClearPathCache();
     BOOST_CHECK_EQUAL(dd_norm, args.GetDataDirBase());
-#endif
 }
 
 BOOST_AUTO_TEST_CASE(util_check)