Try to enable building the LwIP demo on Travis-CI

.travis.yml

@@ -9,3 +9,8 @@ before_install:
 script:
   - chmod +x tools/travis/script.sh
   - ./tools/travis/script.sh
+
+addons:
+ apt:
+  packages:
+   - p7zip-full

tools/travis/script.sh

@@ -4,6 +4,10 @@ set -ex
 
 export PATH=/tmp/gcc-arm-none-eabi-4_9-2015q3/bin:$PATH
 
+pushd ../ChibiOS-RT/ext
+7z e lwip-2.0.3-patched.7z
+popd
+
 git checkout -- .
 git clean -xfd
 make -C demos/TIVA/RT-TM4C123G-LAUNCHPAD
@@ -12,10 +16,9 @@ git checkout -- .
 git clean -xfd
 make -C demos/TIVA/RT-TM4C1294-LAUNCHPAD
 
-# This demo needs LWIP, it is disabled for now.
-# git checkout -- .
-# git clean -xfd
-# make -C demos/TIVA/RT-TM4C1294-LAUNCHPAD-LWIP
+git checkout -- .
+git clean -xfd
+make -C demos/TIVA/RT-TM4C1294-LAUNCHPAD-LWIP
 
 git checkout -- .
 git clean -xfd