CMakeProjectManager: Use CMAKE_HOME_DIRECTORY as source directory

The CMakeCache.txt file has CMAKE_HOME_DIRECTORY pointing to the
project source directory used to configure the project.

When importing a cmake build the CMAKE_HOME_DIRECTORY from
CMakeCache.txt might not point to the same CMakeLists.txt that was
opened as a project.

qt-cmake-standalone-test from Qt6 uses a CMake template project which
does a add_subdirectory with the test source directory, which will not
work if opened standalone.

Normally this is a user error though, so ask the user if this was
intended, before actually importing the build.

Task-number: QTBUG-88776
Change-Id: Ifdd5e1d1cb8a1ef9955d22493eba3a1a55dc689f
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/cmakeprojectmanager/builddirparameters.cpp

@@ -27,6 +27,7 @@
 
 #include "cmakebuildconfiguration.h"
 #include "cmakekitinformation.h"
+#include "cmakeprojectconstants.h"
 #include "cmakeprojectplugin.h"
 #include "cmakespecificsettings.h"
 #include "cmaketoolmanager.h"
@@ -67,7 +68,9 @@ BuildDirParameters::BuildDirParameters(CMakeBuildConfiguration *bc)
 
     projectName = p->displayName();
 
-    sourceDirectory = p->projectDirectory();
+    sourceDirectory = bc->sourceDirectory();
+    if (sourceDirectory.isEmpty())
+        sourceDirectory = p->projectDirectory();
     buildDirectory = bc->buildDirectory();
 
     environment = bc->environment();