[partition] Reduce warnings

- Add a helper header that munges the warnings-settings so that
  KPMcore headers can be included.

src/libcalamares/partition/KPMHelper.h

@@ -0,0 +1,36 @@
+/* === This file is part of Calamares - <https://calamares.io> ===
+ *
+ *   SPDX-FileCopyrightText: 2020 Adriaan de Groot <groot@kde.org>
+ *   SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   Calamares is Free Software: see the License-Identifier above.
+ *
+ */
+
+/*
+ * KPMCore header file inclusion.
+ *
+ * Includes the system KPMCore headers without warnings (by switching off
+ * the expected warnings).
+ */
+#ifndef PARTITION_KPMHELPER_H
+#define PARTITION_KPMHELPER_H
+
+// The kpmcore headers are not C++17 warning-proof, especially
+// with picky compilers like Clang 10. Since we use Clang for the
+// find-all-the-warnings case, switch those warnings off for
+// the we-can't-change-them system headers.
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdocumentation"
+#pragma clang diagnostic ignored "-Wsuggest-destructor-override"
+#endif
+
+#include <backend/corebackend.h>
+#include <fs/filesystemfactory.h>
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
+#endif

src/modules/partition/tests/PartitionJobTests.cpp

@@ -15,14 +15,12 @@
 #include "jobs/CreatePartitionTableJob.h"
 #include "jobs/ResizePartitionJob.h"
 
+#include "partition/KPMHelper.h"
 #include "partition/KPMManager.h"
 #include "partition/PartitionQuery.h"
 #include "utils/Logger.h"
 #include "utils/Units.h"
 
-#include <backend/corebackend.h>
-#include <fs/filesystemfactory.h>
-
 #include <QEventLoop>
 #include <QProcess>
 #include <QtTest/QtTest>