Fail the build early if cmake cannot generate the Makefiles.

.travis.yml

@@ -84,6 +84,8 @@ before_script:
     - ccache -s
     - sed -i "s/-march=native//" CMakeLists.txt
     - mkdir build
+
+script:
   - >
       eval "ARCH_FLAGS=\${ARCH_FLAGS_${ARCH}}" ;
       (cd build && cmake
@@ -93,8 +95,6 @@ before_script:
       -DCMAKE_CXX_FLAGS="$ARCH_FLAGS $GCOV_FLAGS"
       -DCMAKE_EXE_LINKER_FLAGS=$GCOV_FLAGS
       ..)
-
-script:
   - cd build
   - make tests
   - make examples