travis: build astyle and run scripts/check_format.sh

It is small and quick enough to just build the version of astyle we
need.

Only build astyle when configured to use GCC, since the astyle Makefile
is hard-coded to use g++, and we don't need to check style twice anyway.

Change-Id: I9c61bcac80b581f6d72ed7fbc337c5681bf014fc
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>

.travis.yml

@@ -16,6 +16,14 @@ addons:
 
 before_script:
   - export MAKEFLAGS="-j$(nproc)"
+  - if [ "$CC" = gcc ]; then
+      wget https://downloads.sourceforge.net/project/astyle/astyle/astyle%203.0/astyle_3.0_linux.tar.gz;
+      tar xf astyle_3.0_linux.tar.gz;
+      pushd astyle/build/gcc;
+      make;
+      export PATH=$PWD/bin:$PATH;
+      popd;
+    fi
   - wget http://fast.dpdk.org/rel/dpdk-17.02.tar.xz
   - tar xf dpdk-17.02.tar.xz
   - pushd dpdk-17.02
@@ -28,5 +36,6 @@ before_script:
   - popd
 
 script:
+  - ./scripts/check_format.sh
   - make CONFIG_WERROR=y
   - ./unittest.sh