Downgrading warning messages when optional deps are not found.

- Now when find_package() is called for a dependency without the
  REQUIRED or QUIET qualifiers, we emit no priority (above STATUS, but
  below WARNING) messages and continue.

Change-Id: I8cdeda7a8f6c91d45fb7f24fb366244c6c9b66e1

cmake/FindSuiteSparse.cmake

diff --git a/cmake/FindSuiteSparse.cmake b/cmake/FindSuiteSparse.cmake
index 20c3161..3f3a50d 100644
--- a/cmake/FindSuiteSparse.cmake
+++ b/cmake/FindSuiteSparse.cmake
@@ -128,9 +128,9 @@
   ELSEIF (SuiteSparse_FIND_REQUIRED)
     MESSAGE(FATAL_ERROR "Failed to find SuiteSparse - " ${REASON_MSG} ${ARGN})
   ELSE()
-    # Neither QUIETLY nor REQUIRED, use WARNING which emits a message
+    # Neither QUIETLY nor REQUIRED, use no priority which emits a message
     # but continues configuration and allows generation.
-    MESSAGE(WARNING "Failed to find SuiteSparse - " ${REASON_MSG} ${ARGN})
+    MESSAGE("-- Failed to find SuiteSparse - " ${REASON_MSG} ${ARGN})
   ENDIF (SuiteSparse_FIND_QUIETLY)
 ENDMACRO(SUITESPARSE_REPORT_NOT_FOUND)