travis: improve build process and expand build matrix

Make a build heriarchy to reduce images size.
Add Android Things builds to build matrix.
Drop gcc-4 builds, use gcc-5 and gcc-6 instead.
Add SonarQube static analysis scans.

Signed-off-by: Nicolas Oliver <dario.n.oliver@intel.com>

.travis.yml

@@ -1,12 +1,11 @@
+dist: trusty
 sudo: required
 
 language: cpp
 
 compiler:
   - clang
-  - gcc-4.8
   - gcc
-  - gcc-6
 
 env:
   - TARGET=doc
@@ -15,6 +14,33 @@ env:
   - TARGET=node4
   - TARGET=node5
   - TARGET=node6
+  - TARGET=android
+  - TARGET=sonar-scan
+
+matrix:
+  exclude:
+    - compiler: clang
+      env: TARGET=java
+    - compiler: gcc
+      env: TARGET=android
+    - compiler: clang
+      env: TARGET=sonar-scan
+  include:
+    - compiler: gcc
+      env: GCC_VERSION=6 TARGET=doc
+    - compiler: gcc
+      env: GCC_VERSION=6 TARGET=python
+    - compiler: gcc
+      env: GCC_VERSION=6 TARGET=java
+    - compiler: gcc
+      env: GCC_VERSION=6 TARGET=node4
+    - compiler: gcc
+      env: GCC_VERSION=6 TARGET=node5
+    - compiler: gcc
+      env: GCC_VERSION=6 TARGET=node6
+  allow_failures:
+    - compiler: gcc
+      env: TARGET=sonar-scan
 
 services:
   - docker
@@ -26,12 +52,12 @@ before_install:
   - sudo mv docker-compose /usr/local/bin
 
 before_script:
-  - if [ "$CC" == "gcc-4.8" ]; then export CC=gcc-4.8; fi
-  - if [ "$CXX" == "g++-4.8" ]; then export CXX=g++-4.8; fi
-  - if [ "$CC" == "gcc-6" ]; then export CC=gcc-6; fi
-  - if [ "$CXX" == "g++-6" ]; then export CXX=g++-6; fi
+  - if [ "$CC" == "gcc" ]; then export CC=gcc-${GCC_VERSION:-5}; fi
+  - if [ "$CXX" == "g++" ]; then export CXX=g++-${GCC_VERSION:-5}; fi
   - if [ "$CC" == "clang" ]; then export CC=clang-3.8; fi
   - if [ "$CXX" == "clang++" ]; then export CXX=clang++-3.8; fi
+  - docker-compose build base
+  - if [ "$TARGET" == "android" ]; then docker-compose build java; fi
   - docker-compose build ${TARGET}
 
 script: