travis: attempt to fix Ubuntu build

.travis.yml

-sudo: required
+sudo: false
 
 services:
   - docker
@@ -18,14 +18,16 @@ addons:
 before_install:
   - echo $LANG
   - echo $LC_ALL
-  - if [ $TRAVIS_OS_NAME == linux ]; then git clone https://github.com/msgpack/msgpack-c.git && cd msgpack-c && mkdir build && cmake .. && make -j && sudo make install; fi
+  - if [ $TRAVIS_OS_NAME == linux ]; then git clone https://github.com/msgpack/msgpack-c.git && cd msgpack-c && mkdir build && cmake -DCMAKE_INSTALL_PREFIX=$HOME/usr .. && make -j && make install; fi
   - if [ $TRAVIS_OS_NAME == osx ]; then brew update && brew install llvm36 && brew install msgpack && brew install gnutls && brew link --force llvm36; fi
 
 before_script:
-  - if [ $TRAVIS_OS_NAME == linux ]; then travis_retry ./autogen.sh && ./configure; fi
+  - if [ $TRAVIS_OS_NAME == linux ]; then travis_retry ./autogen.sh && ./configure --prefix=$HOME/usr; fi
   - if [ $TRAVIS_OS_NAME == osx ]; then travis_retry ./autogen.sh && ./configure; fi
 
-script: make -j
+script:
+  - ls -R $HOME/usr
+  - make -j
 
 notifications:
   email: