Support Temporary Directory on different Drive

If Project and Temporary Directory are located on different
Windows drives (i.e. D:\ and C:\) an exception was thrown
in the past.

headlock/integrations/pytest/plugin_headlock_debug.py

@@ -218,8 +218,10 @@ def build(self, additonal_c_sources=None):
         if master_cmakelist:
             master_cmakelist_path = Path(master_cmakelist)
             master_cmakelist_dir = master_cmakelist_path.parent.resolve()
-            rel_build_dir = os.path.relpath(self.build_dir,
-                                            str(master_cmakelist_dir))
+            try:
+                rel_build_dir = self.build_dir.relative_to(master_cmakelist_dir)
+            except ValueError:
+                rel_build_dir = self.build_dir.absolute()
             rel_build_dir_str = str(rel_build_dir).replace('\\', '/')
             if master_cmakelist_path.exists():
                 lines = master_cmakelist_path.open().readlines()