arm-unknown-linux-musleabi is only supported on Rust 1.14+

Author: Susurrus

.travis.yml

@@ -131,7 +131,7 @@ matrix:
     - env: TARGET=mips64el-unknown-linux-gnuabi64
       rust: 1.13.0
     - env: TARGET=arm-unknown-linux-musleabi
-      rust: 1.13.0
+      rust: 1.14.0
     - env: TARGET=s390x-unknown-linux-gnu
       rust: 1.13.0