Fixes #337 ("New -Wundef warning")

Author: igaztanaga

include/boost/container/detail/workaround.hpp

@@ -249,12 +249,12 @@ namespace boost {
     #define BOOST_CONTAINER_NOVTABLE
 #endif
 
-#if (defined(BOOST_CLANG) && BOOST_CLANG_VERSION >= 30600)
+#if defined(BOOST_CLANG) && defined(BOOST_CLANG_VERSION) && (BOOST_CLANG_VERSION >= 30600)
 
   #define BOOST_CONTAINER_UNROLL_PRAGMA(x) _Pragma(#x)
   #define BOOST_CONTAINER_UNROLL(n) BOOST_CONTAINER_UNROLL_PRAGMA(unroll n)
 
-#elif (defined(BOOST_GCC) && BOOST_GCC_VERSION >= 150000)
+#elif defined(BOOST_GCC) && defined(BOOST_GCC_VERSION) && (BOOST_GCC_VERSION >= 150000)
   // GCC < 15 emits an unsuppressible "ignoring loop annotation" warning
   // when the optimizer decides it cannot unroll a loop (complex iterators,
   // unknown trip count, etc.). This was fixed in GCC 15.