BUG: CMake cache variable must be unset before compile check, otherwise it...

BUG: CMake cache variable must be unset before compile check, otherwise it does not get updated in subsequent configuration steps (fix bugs #1376)

CMake/OTBCheckCpp11Keywords.cmake

@@ -22,6 +22,8 @@ include(CheckCXXSourceCompiles)
 
 set(CMAKE_REQUIRED_FLAGS ${CMAKE_CXX_FLAGS})
 
+unset(OTB_HAS_CXX11 CACHE)
+
 CHECK_CXX_SOURCE_COMPILES("
 #ifdef _MSC_VER
   #if _MSC_VER <= 1700