Buildsystem: Fix a logical error in git revision-detection, and also

make the warning text a little bit more "Hello Cpt.Obvious" obvious for
users that can't read. (It now includes the word WARNING in the warnings)

cmake/showoptions.cmake

@@ -1,6 +1,5 @@
 # output generic information about the core and buildtype chosen
 
-message("")
 message("* TrinityCore revision   : ${rev_id_str} (${rev_hash_str})")
 if( UNIX )
   message("* Build binaries in      : ${CMAKE_BUILD_TYPE} mode")