GenericProjectManager: Do not make every subdir an include dir

Large projects can have thousands of subdirectories, only a tiny subset
of which are supposed to be include directories. Use the directory name
as a heuristic instead.

Fixes: QTCREATORBUG-29099
Change-Id: I207ea2b7d2739c4f6c27fa96865dfde2570caf8a
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/genericprojectmanager/genericproject.cpp

@@ -330,8 +330,9 @@ bool GenericBuildSystem::addFiles(Node *, const FilePaths &filePaths_, FilePaths
     QSet<QString> toAdd;
 
     for (const QString &filePath : filePaths) {
-        const QString directory = QFileInfo(filePath).absolutePath();
-        if (!includes.contains(directory))
+        const QFileInfo fi(filePath);
+        const QString directory = fi.absolutePath();
+        if (fi.fileName() == "include" && !includes.contains(directory))
             toAdd << directory;
     }