Buildsystem: Removed handling for -DPREFIX shortcut for -DCMAKE_INSTALL_PREFIX cmake option, it an internal cmake variable since version 3.2

(cherry picked from commit 1987d3187d1f14cf6dfcaf4f63861db806ad06cc)

cmake/macros/CheckPlatform.cmake

@@ -7,8 +7,6 @@ else()
     MESSAGE(STATUS "Detected 32-bit platform")
 endif()
 
-include("${CMAKE_SOURCE_DIR}/cmake/platform/settings.cmake")
-
 if(WIN32)
   include("${CMAKE_SOURCE_DIR}/cmake/platform/win/settings.cmake")
 elseif(UNIX)

cmake/platform/settings.cmake

@@ -1,5 +0,0 @@
-# set installation prefix
-if( PREFIX )
-  set(CMAKE_INSTALL_PREFIX "${PREFIX}")
-endif()
-