fixing THPP cmake for cmake < 3.1 (pytorch#559)

Author: soumith

torch/lib/THPP/CMakeLists.txt

@@ -1,4 +1,4 @@
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
+CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
 SET(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake ${CMAKE_MODULE_PATH})
 
 ################################################################################
@@ -18,6 +18,14 @@ FUNCTION(EXCLUDE_DIR list_name dir_name)
 ENDFUNCTION()
 
 ################################################################################
+    
+if(${CMAKE_VERSION} VERSION_LESS "2.8.12")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+else(${CMAKE_VERSION} VERSION_LESS "2.8.12")
+  if(${CMAKE_VERSION} VERSION_LESS "3.1")
+    add_compile_options(-std=c++11) # CMake 2.8.12 to 3.1
+  endif(${CMAKE_VERSION} VERSION_LESS "3.1")
+endif(${CMAKE_VERSION} VERSION_LESS "2.8.12")
 
 IF(NOT Torch_FOUND)
   FIND_PACKAGE(Torch REQUIRED)
@@ -40,9 +48,12 @@ EXCLUDE_DIR(all_cpp ".*/generic/.*\\.cpp$")
 
 INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR})
 ADD_LIBRARY(THPP SHARED ${all_cpp})
-SET_PROPERTY(TARGET THPP PROPERTY CXX_STANDARD 11)
 SET_TARGET_PROPERTIES(THPP PROPERTIES VERSION 1 SOVERSION 1)
 
+if(NOT ${CMAKE_VERSION} VERSION_LESS "3.1")
+    SET_PROPERTY(TARGET THPP PROPERTY CXX_STANDARD 11)
+endif(NOT ${CMAKE_VERSION} VERSION_LESS "3.1")
+
 TARGET_LINK_LIBRARIES(THPP PRIVATE ${TH_LIBRARIES})
 
 INSTALL(TARGETS THPP