Use target cmake variables instead of host variables

Author: isuruf

CMakeLists.txt

@@ -29,8 +29,8 @@ if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
   project(Flang)
 endif()
 
-set(TARGET_OS ${CMAKE_HOST_SYSTEM_NAME} CACHE STRING "Target OS")
-set(TARGET_ARCHITECTURE ${CMAKE_HOST_SYSTEM_PROCESSOR} CACHE STRING "Target Architecture")
+set(TARGET_OS ${CMAKE_SYSTEM_NAME} CACHE STRING "Target OS")
+set(TARGET_ARCHITECTURE ${CMAKE_SYSTEM_PROCESSOR} CACHE STRING "Target Architecture")
 
 if (POLICY CMP0054)
   cmake_policy(SET CMP0054 NEW)