(kbuild) Fix missing cros:// defconfig

In configuration where cros:// config is defconfig,
node will have incorrect entry for config_full, missing
cross:// (defconfig) part.

Signed-off-by: Denys Fedoryshchenko <denys.f@collabora.com>

Author: nuclearcat

kernelci/kbuild.py

@@ -576,6 +576,7 @@ def _merge_frags(self, fragnum):
                     self._getcrosfragment(self._defconfig)
                 f.write(content)
             self.addcmd("make olddefconfig")
+            self._config_full = self._defconfig + self._config_full
         else:
             if isinstance(self._defconfig, str):
                 self.addcmd("make " + self._defconfig)