travis: Correctly minimize build matrix

.travis.yml

@@ -31,17 +31,29 @@ env:
   # COVERITY_SCAN_TOKEN
     - secure: "lZ7pHQvl5dpZWzBQAaIMf0wqrvtcZ4wiZKeIZjf83TEsflW8+z0uTpIuN30ZV6Glth/Sq1OhLnTP5+N57fZU/1ebA5twHdvP4bS5CIUUg71/CXQZNl36xeaqvxsG/xRrdpKOsPdjAOsQ9KPTQulsX43XDLS7CasMiLvYOpqKcPc="
     - PV=r8e PLATF=linux-x86_64 NDK_HOME=${TRAVIS_BUILD_DIR}/android-ndk-${PV} PATH=${PATH}:${NDK_HOME}
-  matrix:
-    - os: linux LINUX=1 TRAVIS_NO_EXPORT=YES ENABLE_COVERALLS=ON
+
+matrix:
+  exclude:
+    - os: linux
+      env:
+
+  include:
+    - os: linux
       compiler: gcc
-    - os: linux LINUX=1 TRAVIS_NO_EXPORT=NO  ENABLE_COVERALLS=OFF
-      compiler: clang
-    - os: linux LINUX=1 SHARED_BUILD=ON TRAVIS_NO_EXPORT=NO  ENABLE_COVERALLS=OFF
+      env: LINUX=1 TRAVIS_NO_EXPORT=YES ENABLE_COVERALLS=ON
+    - os: linux
       compiler: gcc
-    - os: linux LINUX=1 SHARED_BUILD=ON TRAVIS_NO_EXPORT=NO  ENABLE_COVERALLS=OFF
-      compiler: clang
+      env: LINUX=1 TRAVIS_NO_EXPORT=NO  ENABLE_COVERALLS=OFF
+    - os: linux
+      compiler: gcc
+      env: LINUX=1 SHARED_BUILD=ON TRAVIS_NO_EXPORT=NO  ENABLE_COVERALLS=OFF
+    - os: linux
+      compiler: gcc
+      env: LINUX=1 SHARED_BUILD=ON TRAVIS_NO_EXPORT=NO  ENABLE_COVERALLS=OFF
     - os: osx
+      compiler: clang
       osx_image: xcode8.2
+      env:
 
 install:
   - if [ $ANDROID ]; then wget -c http://dl.google.com/android/ndk/android-ndk-${PV}-${PLATF}.tar.bz2 && tar xf android-ndk-${PV}-${PLATF}.tar.bz2 ; fi