fix #918 (use COPYING.LIB instead of COPYING for libiconv)

Author: henderkes

config/source.json

@@ -537,7 +537,7 @@
         "provide-pre-built": true,
         "license": {
             "type": "file",
-            "path": "COPYING"
+            "path": "COPYING.LIB"
         }
     },
     "libiconv-win": {