- enabled LTO if supported

src/CMakeLists.txt

@@ -1,9 +1,11 @@
-cmake_minimum_required (VERSION 2.6)
+cmake_minimum_required (VERSION 3.9.4)
 project (checkit_tiff)
 include_directories("${PROJECT_SOURCE_DIR}/headers")
 include_directories("${PROJECT_SOURCE_DIR}/validate_icc")
 include (CheckSymbolExists)
 include (CheckFunctionExists)
+include(CheckIPOSupported)
+
 
 file( GLOB checkit_tiff_SOURCES 
   "${PROJECT_SOURCE_DIR}/tagrules/*.c"
@@ -49,6 +51,14 @@ else()
   message(STATUS "Your compiler (${CMAKE_C_COMPILER}) has no gnu11 support. If you are using clang on Apple OS X, please switch to gcc (version > 4.7) which is compliant with the C11 standard.")
 endif()
 
+check_ipo_supported(RESULT LTO_IS_SUPPORTED OUTPUT LTO_CHECK_ERROR)
+if (LTO_IS_SUPPORTED)
+  message(STATUS "IPO / LTO enabled")
+  SET(INTERPROCEDURAL_OPTIMIZATIONS TRUE)
+else()
+  message(STATUS "IPO / LTO unsupported: <${LTO_CHECK_ERROR}>")
+endif()
+
 if(WIN32)
   add_definitions(-D__WIN32__=1)
   SET(CMAKE_FIND_LIBRARY_SUFFIXES ".a")