Try to fix travis

.travis.yml

@@ -12,16 +12,14 @@ env:
     - USE_CCACHE=1
     - PROTOBUF_ROOT=$HOME/protobuf
 before_install: |
-  if [[ $TRAVIS_OS_NAME == 'linux' ]]; then
-    # protoc
-    if [ -d $PROTOBUF_ROOT ]; then
-      mkdir -p $PROTOBUF_ROOT
-      pushd $PROTOBUF_ROOT
-      wget https://github.com/google/protobuf/releases/download/v3.1.0/protoc-3.1.0-linux-x86_64.zip
-      unzip protoc-3.1.0-linux-x86_64.zip
-      popd
-      export PATH=$PROTOBUF_ROOT/bin:$PATH
-    fi
+  export PATH=$PROTOBUF_ROOT/bin:$PATH
+  if ! [ -x $PROTOBUF_ROOT/bin/protoc ]; then
+    rm -rf $PROTOBUF_ROOT
+    mkdir -p $PROTOBUF_ROOT
+    pushd $PROTOBUF_ROOT
+    wget https://github.com/google/protobuf/releases/download/v3.1.0/protoc-3.1.0-linux-x86_64.zip
+    unzip protoc-3.1.0-linux-x86_64.zip
+    popd
   fi
 install:
  - mkdir -p $HOME/.ccache
@@ -29,6 +27,7 @@ install:
  - go get -u github.com/jteeuwen/go-bindata/...
  - go get -d github.com/ry/v8worker2
  - (cd $GOPATH/src/github.com/ry/v8worker2 && ./tools/build.py)
+ - yarn
 script:
  - yarn lint-version
  - make lint