Make faster Travis.

.travis.yml

@@ -5,23 +5,29 @@ go:
   - 1.5
   - 1.6
   - tip
-
 env:
   - LIBWEBP_VERSION="0.4.1"
   - LIBWEBP_VERSION="0.4.2"
   - LIBWEBP_VERSION="0.4.3"
   - LIBWEBP_VERSION="0.5.0"
 
+cache:
+  directories:
+    - $HOME/cache
+sudo: false
+
 before_install:
-  - sudo apt-get update -qq
-  - sudo apt-get install -qq libjpeg-dev libpng-dev libtiff-dev libgif-dev
   - >
+      test -e $HOME/cache/libwebp-${LIBWEBP_VERSION}/lib/libwebp.so || (
       cd /tmp
       && wget http://downloads.webmproject.org/releases/webp/libwebp-${LIBWEBP_VERSION}.tar.gz
       && tar xf libwebp-${LIBWEBP_VERSION}.tar.gz
       && cd libwebp-${LIBWEBP_VERSION}
-      && ./configure
+      && ./configure --prefix=$HOME/cache/libwebp-${LIBWEBP_VERSION}
       && make
-      && sudo make install
+      && make install
+      )
   - cd $HOME/gopath/src/github.com/harukasan/go-libwebp
-  - export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH
+  - export CGO_CFLAGS="-I $HOME/cache/libwebp-${LIBWEBP_VERSION}/include"
+  - export CGO_LDFLAGS="-L $HOME/cache/libwebp-${LIBWEBP_VERSION}/lib"
+  - export LD_LIBRARY_PATH=$HOME/cache/libwebp-${LIBWEBP_VERSION}/lib:$LD_LIBRARY_PATH