[docker] upgrade docker scripts [skip ci]

docker/linux/Dockerfile

@@ -1,7 +1,7 @@
 FROM mapbox/gl-native:travis
 
 # Install compiler
-RUN apt-get -y install gdb g++-4.9 gcc-4.9 libllvm3.4
+RUN apt-get -y install gdb g++-5 gcc-5 libllvm3.4
 
 RUN useradd -ms /bin/bash mapbox
 USER mapbox
@@ -11,4 +11,4 @@ WORKDIR /home/mapbox
 # Node
 RUN git clone https://github.com/creationix/nvm.git ~/.nvm && \
     . ~/.nvm/nvm.sh && \
-    NVM_DIR=~/.nvm nvm install 0.10
+    NVM_DIR=~/.nvm nvm install 4.4.5

docker/linux/test.sh

@@ -3,12 +3,13 @@
 # set -e
 # set -o pipefail
 
-export CXX=g++-4.9
+export _CXX=g++-5
+export _CC=gcc-5
 export BUILDTYPE=Release
 
 # Node
 . ~/.nvm/nvm.sh
-nvm use 0.10
+nvm use 4.4.5
 
 # Xvfb
 start-stop-daemon --start --pidfile ~/xvfb.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -screen 0 1024x768x24 -ac +extension GLX +render -noreset
@@ -17,9 +18,7 @@ cd build
 
 # before_install
 source ./scripts/travis_helper.sh
+source ./scripts/travis_setup.sh
 
-# install
-./platform/linux/scripts/install.sh
-
-# script
-./platform/linux/scripts/run.sh
+make linux
+make test-linux