Use manually-created temp dirs

Using t.TempDir() may be failing on Windows due to removals.

snapshot/upgrader_test.go

@@ -27,8 +27,12 @@ func Test_Upgrade_OK(t *testing.T) {
 	logger := log.New(os.Stderr, "[snapshot-store-upgrader] ", 0)
 	v7Snapshot := "testdata/upgrade/v7.20.3-snapshots"
 	v7SnapshotID := "2-18-1686659761026"
-	oldTemp := filepath.Join(t.TempDir(), "snapshots")
-	newTemp := filepath.Join(t.TempDir(), "rsnapshots")
+	oldTemp := mustMakeTempDir()
+	defer os.RemoveAll(oldTemp)
+	newTemp := mustMakeTempDir()
+	defer os.RemoveAll(newTemp)
+	oldTemp = filepath.Join(oldTemp, "snapshots")
+	newTemp = filepath.Join(newTemp, "rsnapshots")
 
 	// Copy directory because succeessful test runs will delete it.
 	copyDir(v7Snapshot, oldTemp)
@@ -199,3 +203,11 @@ func copyDir(src string, dst string) (err error) {
 
 	return
 }
+
+func mustMakeTempDir() string {
+	dir, err := os.MkdirTemp("", "rsnapshots-upgrade-test")
+	if err != nil {
+		panic(err)
+	}
+	return dir
+}