CMake: add backward compatibility

CMakeLists.txt

@@ -2,8 +2,8 @@
 ## Author: Hank Anderson <hank@statease.com>
 ##
 
-cmake_minimum_required(VERSION 3.9) # CMP0069 NEW
-include(CheckIPOSupported)
+cmake_minimum_required(VERSION 2.8.5)
+
 project(OpenBLAS C ASM)
 set(OpenBLAS_MAJOR_VERSION 0)
 set(OpenBLAS_MINOR_VERSION 3)
@@ -148,10 +148,14 @@ endif()
 # add objects to the openblas lib
 add_library(${OpenBLAS_LIBNAME} ${LA_SOURCES} ${LAPACKE_SOURCES} ${RELA_SOURCES} ${TARGET_OBJS} ${OpenBLAS_DEF_FILE})
 
-check_ipo_supported(RESULT IPO_SUPPORTED)
-if(IPO_SUPPORTED)
-  message(STATUS "Building with link-time code generation")
-  set_property(TARGET ${OpenBLAS_LIBNAME} PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
+if(POLICY CMP0990)
+  cmake_policy(SET CMP0990 NEW)
+  include(CheckIPOSupported)
+  check_ipo_supported(RESULT IPO_SUPPORTED)
+  if(IPO_SUPPORTED)
+    message(STATUS "Building with link-time code generation")
+    set_property(TARGET ${OpenBLAS_LIBNAME} PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
+  endif()
 endif()
 
 # Android needs to explicitly link against libm