Utils: Introduce FilePath::is{Relative,Absolute}Path

To operate correctly with remote target files systems that do not
match the host OS.

Change-Id: Ia4ea284dc38399deacb50410c9618e1e139f4e13
Reviewed-by: David Schulz <david.schulz@qt.io>

src/libs/utils/fileutils.h

@@ -143,6 +143,9 @@ public:
     bool isExecutableFile() const;
     bool isReadableFile() const;
     bool isReadableDir() const;
+    bool isRelativePath() const;
+    bool isAbsolutePath() const { return !isRelativePath(); }
+
     bool createDir() const;
     QList<FilePath> dirEntries(const QStringList &nameFilters,
                                QDir::Filters filters,