Close exit_code file handle

Author: UtterVitriol

lua/cmake-tools/terminal.lua

@@ -580,7 +580,9 @@ local get_last_exit_code = function()
     print("Could not find last tmp file conaining exit code")
     return nil
   end
-  return tonumber(file:read("*n"))
+  local code = tonumber(file:read("*n"))
+  file:close()
+  return code
 end
 
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