CI/tests: enable test target on TravisCI for CMake builds

Added test-nonflaky target to CMake builds

Disabled test 1139 because the cmake build doesn't create docs/curl.1

Closes #6074

scripts/travis/script.sh

@@ -106,6 +106,7 @@ fi
 if [ "$T" = "cmake" ]; then
   cmake -H. -Bbuild -DCURL_WERROR=ON $C
   cmake --build build
+  env TFLAGS="!1139" cmake --build build --target test-nonflaky
 fi
 
 if [ "$T" = "distcheck" ]; then