CMake: libyaml is required; improve msg

pub/cmake/modules/FindLibyaml.cmake

@@ -56,10 +56,10 @@ find_library(LIBYAML_LIBRARY
     /opt/local
     /opt/csw
     /opt
+    REQUIRED
     )
 
 message(STATUS
-    "libyaml: FOUND=${LIBYAML_FOUND}, VERSION=${LIBYAML_VERSION}, LIB=${LIBYAML_LIBRARY}")
+    "libyaml: found LIB=${LIBYAML_LIBRARY}, VERSION=${LIBYAML_VERSION}")
 
-message(STATUS "Found FindLibyaml: ${LIBYAML_LIBRARY}")
 mark_as_advanced(LIBYAML_INCLUDE_DIR LIBYAML_LIBRARY)