qstorageinfo_p.h: fix -Wunused-function

Make shouldIncludeFs() class- instead of file-static by moving it into
QStorageInfoPrivate. Ditto isParentOf().

Put the functions under Q_OS_UNIX.

Fixes Clang -Wunused-function, and removes a non-q/Q-prefixed name
from the global namespace.

Amends 543ae6e.

Manual conflict resolution for 6.8:
- tracked a user of shouldIncludeFs() that needs a QStorageInfoPrivate::
  prefix added from qstorageinfo_linux.cpp to qstorageinfo_linux_p.h

Pick-to: 6.7
Task-number: QTBUG-77059
Task-number: QTBUG-126219
Change-Id: I4cc62ae044d74919d73d08f6ce3ad57f2e00b4c8
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 5cd154d)
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
Reviewed-by: Lena Biliaieva <lena.biliaieva@qt.io>

src/corelib/io/qstorageinfo_linux_p.h

@@ -215,7 +215,8 @@ doParseMountInfo(const QByteArray &mountinfo, FilterMountInfo filter = FilterMou
             continue;
         info.fsType = fields[FsType].toByteArray();
 
-        if (filter == FilterMountInfo::Filtered && !shouldIncludeFs(info.mountPoint, info.fsType))
+        if (filter == FilterMountInfo::Filtered
+                && !QStorageInfoPrivate::shouldIncludeFs(info.mountPoint, info.fsType))
             continue;
 
         std::optional<dev_t> devno = deviceNumber(fields[DevNo]);

src/corelib/io/qstorageinfo_p.h

@@ -90,6 +90,18 @@ class QStorageInfoPrivate : public QSharedData
     void retrieveVolumeInfo();
 #endif
 
+#ifdef Q_OS_UNIX
+    // Common helper functions
+    template <typename String>
+    static bool isParentOf(const String &parent, const QString &dirName)
+    {
+        return dirName.startsWith(parent) &&
+                (dirName.size() == parent.size() || dirName.at(parent.size()) == u'/' ||
+                 parent.size() == 1);
+    }
+    static inline bool shouldIncludeFs(const QString &mountDir, const QByteArray &fsType);
+#endif
+
 public:
     QString rootPath;
     QByteArray device;
@@ -107,16 +119,8 @@ class QStorageInfoPrivate : public QSharedData
     bool valid = false;
 };
 
-// Common helper functions
-template <typename String>
-static bool isParentOf(const String &parent, const QString &dirName)
-{
-    return dirName.startsWith(parent) &&
-            (dirName.size() == parent.size() || dirName.at(parent.size()) == u'/' ||
-             parent.size() == 1);
-}
-
-static inline bool shouldIncludeFs(const QString &mountDir, const QByteArray &fsType)
+#ifdef Q_OS_UNIX
+bool QStorageInfoPrivate::shouldIncludeFs(const QString &mountDir, const QByteArray &fsType)
 {
 #if defined(Q_OS_ANDROID)
     // "rootfs" is the filesystem type of "/" on Android
@@ -158,6 +162,7 @@ static inline bool shouldIncludeFs(const QString &mountDir, const QByteArray &fs
     // size checking in QStorageInfo::mountedVolumes()
     return true;
 }
+#endif // Q_OS_UNIX
 
 QT_END_NAMESPACE