cmake: use GNUInstallDirs to autodetect installation directories (Linux only) (#1474)

* cmake: use GNUInstallDirs to autodetect installation directories (Linux)
Signed-off-by: Artur Wojcik <artur.wojcik@intel.com>

* define LINUX variable to detect Linux
Signed-off-by: Artur Wojcik <artur.wojcik@intel.com>

CMakeLists.txt

@@ -43,6 +43,10 @@ endif()
 
 project (ngraph)
 
+if (UNIX AND NOT APPLE)
+    set(LINUX TRUE)
+endif()
+
 SET(GCC_MIN_VERSION 4.8)
 SET(CLANG_MIN_VERSION 3.8)
 SET(APPLE_CLANG_MIN_VERSION 8.1)
@@ -102,8 +106,14 @@ endif()
 # Installation logic...
 #-----------------------------------------------------------------------------------------------
 
-if (NOT APPLE AND NOT WIN32)
+if (LINUX)
+    include(GNUInstallDirs)
     include(cmake/platform.cmake)
+else()
+    set(CMAKE_INSTALL_BINDIR "bin")
+    set(CMAKE_INSTALL_INCLUDEDIR "include")
+    set(CMAKE_INSTALL_DOCDIR "doc")
+    set(CMAKE_INSTALL_LIBDIR "lib")
 endif()
 
 if (DEFINED NGRAPH_INSTALL_PREFIX)
@@ -112,10 +122,10 @@ endif()
 message(STATUS "Installation directory: ${CMAKE_INSTALL_PREFIX}")
 
 # Destinations
-set(NGRAPH_INSTALL_LIB "${CMAKE_INSTALL_PREFIX}/lib")
-set(NGRAPH_INSTALL_INCLUDE "${CMAKE_INSTALL_PREFIX}/include")
-set(NGRAPH_INSTALL_DOC "${CMAKE_INSTALL_PREFIX}/doc")
-set(NGRAPH_INSTALL_BIN "${CMAKE_INSTALL_PREFIX}/bin")
+set(NGRAPH_INSTALL_LIB "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}")
+set(NGRAPH_INSTALL_INCLUDE "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR}")
+set(NGRAPH_INSTALL_DOC "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_DOCDIR}")
+set(NGRAPH_INSTALL_BIN "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}")
 set(CMAKE_INSTALL_RPATH "$ORIGIN")
 
 #-----------------------------------------------------------------------------------------------