fix

cmake/libraries/boost.cmake

@@ -5,6 +5,7 @@ if(PROJECT_ENABLE_BOOST)
     set(BOOST_MINOR_VERSION ${BOOST2_MINOR_VERSION})
     set(BOOST_PATCH_VERSION ${BOOST2_PATCH_VERSION})
   endif()
+
   set(BOOST_ROOT ${PROJECT_EXTERNAL_BUILD_ROOT})
   set(BOOST_INCLUDE_DIR ${BOOST_ROOT}/include/boost-${BOOST_MINOR_VERSION}_${BOOST_MINOR_VERSION})
 
@@ -126,16 +127,22 @@ if(PROJECT_ENABLE_BOOST)
         address-model=64
         architecture=${BOOST_ARCH}
         cxxstd=${BOOST_CXX_STANDARD}
-        cxxflags=${BOOST_CXX_FLAGS}
-        cflags=${BOOST_C_FLAGS}
         define=BOOST_SYSTEM_NO_DEPRECATED
         link=${BOOST_LINK}
-        linkflags=${BOOST_LINK_FLAGS}
         threading=multi
         variant=${BOOST_BUILD_TYPE_LOWER}
         ${BOOST_OPTIONS}
       )
 
+      if (BOOST_CXX_FLAGS)
+        set(BOOST_BUILD_ARGS
+          ${BOOST_BUILD_ARGS}
+          cflags=${BOOST_C_FLAGS}
+          cxxflags=${BOOST_CXX_FLAGS}
+          linkflags=${BOOST_LINK_FLAGS}
+        )
+      endif()
+
       ExternalProject_Add(boost_project
         PREFIX external
         URL ${PROJECT_3RD_PARTY_DIR}/boost_${BOOST_MAJOR_VERSION}_${BOOST_MINOR_VERSION}_${BOOST_PATCH_VERSION}.tar.gz