make test: fix/disable VAPI tests on centos

Workaround old `check' library on centos.
Disable building/running of C++ VAPI test as centos's gcc can't compile
our C++ code (vapi.hpp) due to bug.

Change-Id: If9da9c7f1bc076f7cdfb9bd3016dfe60a08afa36
Signed-off-by: Klement Sekera <ksekera@cisco.com>
diff --git a/test/ext/Makefile b/test/ext/Makefile
index 6b3cb90..6436302 100644
--- a/test/ext/Makefile
+++ b/test/ext/Makefile
@@ -2,6 +2,10 @@
 CBIN = $(addprefix $(BINDIR), vapi_c_test)
 CPPBIN = $(addprefix $(BINDIR), vapi_cpp_test)
 
+ifeq ($(filter centos,$(OS_ID)),$(OS_ID))
+CPPBIN=
+endif
+
 LIBS = -L$(VPP_TEST_BUILD_DIR)/vpp/.libs/ -L$(VPP_TEST_BUILD_DIR)/vpp/vpp-api/vapi/.libs/ -lvppinfra -lvlibmemoryclient -lsvm -lpthread -lcheck -lsubunit -lrt -lm -lvapiclient
 CFLAGS = -std=gnu99 -g -Wall -pthread -I$(WS_ROOT)/src -I$(VPP_TEST_INSTALL_PATH)/vpp/include -I$(BINDIR)
 CPPFLAGS = -std=c++11 -g -Wall -pthread -I$(WS_ROOT)/src -I$(VPP_TEST_INSTALL_PATH)/vpp/include -I$(BINDIR)