cmake: package_helper: Remove an empty elseif

Cmake complains about this.

Signed-off-by: Wilfried Chauveau <wilfried.chauveau@arm.com>

cmake/package_helper.cmake

@@ -49,7 +49,6 @@ foreach(i RANGE ${CMAKE_ARGC})
   if(CMAKE_ARGV${i} MATCHES "^-B(.*)")
     set(argB ${CMAKE_MATCH_1})
     set(argB_index ${i})
-  elseif()
   elseif(CMAKE_ARGV${i} MATCHES "^-S(.*)")
     set(argS_index ${i})
     set(argS ${CMAKE_MATCH_1})