.travis.yaml,docker-compose.yaml: add examples building to the matrix

Prevent building examples on every job

Signed-off-by: Nicolas Oliver <dario.n.oliver@intel.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

docker-compose.yaml

@@ -22,7 +22,7 @@ services:
         - BUILDSWIGPYTHON=OFF
         - BUILDSWIGJAVA=OFF
         - BUILDSWIGNODE=OFF
-        - BUILDEXAMPLES=ON
+        - BUILDEXAMPLES=OFF
         - IPK=OFF
         - RPM=OFF
         - NPM=OFF
@@ -43,6 +43,13 @@ services:
         - BUILDDOC=ON
     command: make doc
 
+  examples:
+    extends: main
+    build:
+      args:
+        - BUILDEXAMPLES=ON
+    command: bash -c "make $$(make help | grep example | sed 's/... //' | tr '\n' ' ')"
+
   python:
     extends: main
     build: