BUILD: Also test our CMake build system with Travis CI

Note: In the other xoreos repositories, we use gcc for the CMake test.
However, for the main xoreos repository, it fails to link in the
Travis CI Trusty worker, for some reason. It does work on other
systems, so it might be an intermittent gcc bug?

.travis.yml

@@ -8,15 +8,31 @@ compiler:
 
 env:
   global:
-   # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
-   #   via the "travis encrypt" command using the project repo's public key
-   - secure: "oYIV1EmOvP2ruIxyCTPuGuqUsUzTxxu3P+IdlQZgV6aXaBxtFCuoQaLVMOlnx8xSI2V4mb5I/wK5fAtgUAomzDHQmaBNSbJc3xBTy2xgckup60ehKtFqf+ifm+AYcLQQgLtMUDmLNNcJIKUGPZ8GYwjNfWKt3VGuLHV+UFiRuQI="
-   - coverity_scan_run_condition='"$CC" = gcc'
-   - coverity_scan_script_test_mode=false
+    # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
+    #   via the "travis encrypt" command using the project repo's public key
+    - secure: "oYIV1EmOvP2ruIxyCTPuGuqUsUzTxxu3P+IdlQZgV6aXaBxtFCuoQaLVMOlnx8xSI2V4mb5I/wK5fAtgUAomzDHQmaBNSbJc3xBTy2xgckup60ehKtFqf+ifm+AYcLQQgLtMUDmLNNcJIKUGPZ8GYwjNfWKt3VGuLHV+UFiRuQI="
+    - coverity_scan_run_condition='\( "$CC" = gcc \) -a \( $USECMAKE -eq 0 \)'
+    - coverity_scan_script_test_mode=false
+  matrix:
+    # Let's test both our autoconf and CMake build systems
+    - USECMAKE=0
+    - USECMAKE=1
+
+# Only test gcc with autotools, not CMake.
+# We now have three builds: autoconf+gcc, autoconf+clang, CMake+clang
+# Note: In the other xoreos repositories, we use gcc for the CMake test.
+#       However, for the main xoreos repository, it fails to link in
+#       the Travis CI Trusty worker, for some reason. It does work on
+#       other systems, so it might be an intermittent gcc bug?
+matrix:
+  exclude:
+    - compiler: gcc
+      env: USECMAKE=1
 
 script:
-  - if [ "$COVERITY_SCAN_BRANCH" != 1 ]; then ./autogen.sh; fi
-  - if [ "$COVERITY_SCAN_BRANCH" != 1 ]; then ./configure || cat config.log; fi
+  - if [ \( "$COVERITY_SCAN_BRANCH" != 1 \) -a \( $USECMAKE -eq 0 \) ]; then ./autogen.sh; fi
+  - if [ \( "$COVERITY_SCAN_BRANCH" != 1 \) -a \( $USECMAKE -eq 0 \) ]; then ./configure || cat config.log; fi
+  - if [ \( "$COVERITY_SCAN_BRANCH" != 1 \) -a \( $USECMAKE -eq 1 \) ]; then cmake .; fi
   - if [ "$COVERITY_SCAN_BRANCH" != 1 ]; then make -j4; fi
 
 addons: