bump buildrelease for sle15-sp6

Author: dirkmueller

src/bci_build/package/__init__.py

@@ -606,6 +606,8 @@ def build_release(self) -> str | None:
             return "30"
         if "node" in self.build_name:
             return "30"
+        if "base" in self.build_name:
+            return "40"
         if isinstance(self, ApplicationStackContainer):
             return "35"
         return None