CMakePackageConfigHelpers: Remove unused variable

Modules/CMakePackageConfigHelpers.cmake

@@ -522,13 +522,11 @@ function(generate_apple_platform_selection_file _output_file)
   endif()
 
   set(_else ELSE)
-  set(_have_relative 0)
   foreach(_opt IN LISTS _config_file_options _else)
     if(_gpsf_${_opt})
       set(_config_file "${_gpsf_${_opt}}")
       if(NOT IS_ABSOLUTE "${_config_file}")
         string(PREPEND _config_file [[${PACKAGE_PREFIX_DIR}/]])
-        set(_have_relative 1)
       endif()
       set(_branch_${_opt} "include(\"${_config_file}\")")
     elseif(_gpsf_ERROR_VARIABLE)