Update modules for compatibility with CMake 3.12

Author: sethrj

CMakeLists.txt

@@ -88,8 +88,16 @@ if (FLIBCPP_USE_SWIG)
       "and reconfigure.")
   endif()
 
-  cmake_policy(SET CMP0078 "NEW")
-  cmake_policy(SET CMP0086 "NEW")
+  if (CMAKE_VERSION GREATER_EQUAL 3.13)
+    cmake_policy(SET CMP0078 "NEW")
+  else()
+    set(FLIBCPP_CMP0078 "NEW")
+  endif()
+  if (CMAKE_VERSION GREATER_EQUAL 3.14)
+    cmake_policy(SET CMP0086 "NEW")
+  else()
+    set(FLIBCPP_CMP0086 "NEW")
+  endif()
   include(UseSWIG)
 endif()
 

cmake/backport-cmake-318/UseSWIG.cmake

@@ -234,8 +234,12 @@ as well as ``SWIG``:
     set(SWIG_SOURCE_FILE_EXTENSIONS ".i" ".swg")
 #]=======================================================================]
 
-cmake_policy(GET CMP0078 target_name_policy)
-cmake_policy(GET CMP0086 module_name_policy)
+if (CMAKE_VERSION GREATER_EQUAL 3.13)
+  cmake_policy(GET CMP0078 target_name_policy)
+endif()
+if (CMAKE_VERSION GREATER_EQUAL 3.14)
+  cmake_policy(GET CMP0086 module_name_policy)
+endif()
 
 cmake_policy (VERSION 3.12)
 if (target_name_policy)
@@ -466,7 +470,14 @@ function(SWIG_ADD_SOURCE_TO_MODULE name outfiles infile)
     list (APPEND swig_special_flags "-c++")
   endif()
 
-  cmake_policy(GET CMP0086 module_name_policy)
+
+  if (CMAKE_VERSION GREATER_EQUAL 3.14)
+    cmake_policy(GET CMP0086 module_name_policy)
+  elseif(FLIBCPP_CMP0086)
+    set(module_name_policy ${FLIBCPP_CMP0086})
+  else()
+    set(module_name_policy OLD)
+  endif()
   if (module_name_policy STREQUAL "NEW")
     get_source_file_property(module_name "${infile}" SWIG_MODULE_NAME)
     if (module_name)
@@ -616,7 +627,13 @@ function(SWIG_ADD_LIBRARY name)
     unset(_SAM_TYPE)
   endif()
 
-  cmake_policy(GET CMP0078 target_name_policy)
+  if (CMAKE_VERSION GREATER_EQUAL 3.13)
+    cmake_policy(GET CMP0078 target_name_policy)
+  elseif(FLIBCPP_CMP0078)
+    set(target_name_policy ${FLIBCPP_CMP0078})
+  else()
+    set(target_name_policy OLD)
+  endif()
   if (target_name_policy STREQUAL "NEW")
     set (UseSWIG_TARGET_NAME_PREFERENCE STANDARD)
   else()