Compile without debug flags as it trigger an error at link-time (see rust-lang/rust#13213 )

Author: KokaKiwi

.travis.yml

@@ -4,5 +4,5 @@ before_install:
 install:
   - sudo apt-get install rust-nightly
 script:
-  - make
-  - make test
+  - make DEBUG=0
+  - make test DEBUG=0