use gcc as c compiler

yjqg6666 · yjqg6666 · commit 7e09f2fffb9e · 2017-02-07T17:30:43.000+08:00
[skip ci]
diff --git a/.travis.yml b/.travis.yml
@@ -2,6 +2,8 @@ sudo: required
 
 language: c
 
+compiler: gcc
+
 matrix:
     include:
         - os: linux
