Travis: add gcc6 as dependency and use it in ble testing

.travis.yml

@@ -20,6 +20,15 @@ cache:
     - $HOME/.cache/apt
     - $HOME/gcc-arm-none-eabi-6-2017-q2-update
 
+addons:
+  apt:
+    sources:
+      - ubuntu-toolchain-r-test
+    packages:
+      - gcc-6
+      - g++-6
+      - cmake
+
 before_install:
   - bash -c "$STATUS" pending "Local $NAME testing is in progress"
   # Make sure pipefail
@@ -117,7 +126,7 @@ matrix:
 
     - env:
         - NAME=ble-host-tests
-        - BLE_HOST_TESTS=features/FEATURE_BLE/tests
+        - BLE_HOST_TESTS=$PWD/features/FEATURE_BLE/tests
       install:
         # Install dependencies
         - sudo apt-get install cmake
@@ -127,8 +136,10 @@ matrix:
       script:
         # Compile the tests
         - mkdir $BLE_HOST_TESTS/build
-        - cd $BLE_HOST_TESTS/build && cmake .. -G "Unix Makefiles"
-        - make -C $BLE_HOST_TESTS/build
+        - cd $BLE_HOST_TESTS/build && CC=gcc-6 CXX=g++-6 cmake .. -G "Unix Makefiles"
+        - ls $BLE_HOST_TESTS
+        - ls $BLE_HOST_TESTS/build
+        - cd $BLE_HOST_TESTS/build && make 
         # Run ble host tests
         - $BLE_HOST_TESTS/build/gatt-client-tests