travis: Run CPP tests

make/travis.mk

@@ -25,6 +25,10 @@ LIB_RABIT = librabit.a
 # path to libjvm.so
 LIBJVM=$(JAVA_HOME)/jre/lib/amd64/server
 
+# path to googletest and whether to measure coverage or not
+GTEST_PATH =
+WITH_COVER = 1
+
 # List of additional plugins, checkout plugin folder.
 # uncomment the following lines to include these plugins
 # you can also add your own plugin like this