If -fno-strict-overflow is available, don't add -fwrapv

configure.ac

@@ -161,9 +161,10 @@ AS_IF([test "$enable_pie" != "no"],[
   ])
 ])
 
-AX_CHECK_COMPILE_FLAG([-fwrapv], [CFLAGS="$CFLAGS -fwrapv"])
 AX_CHECK_COMPILE_FLAG([-fno-strict-aliasing], [CFLAGS="$CFLAGS -fno-strict-aliasing"])
-AX_CHECK_COMPILE_FLAG([-fno-strict-overflow], [CFLAGS="$CFLAGS -fno-strict-overflow"])
+AX_CHECK_COMPILE_FLAG([-fno-strict-overflow], [CFLAGS="$CFLAGS -fno-strict-overflow"], [
+  AX_CHECK_COMPILE_FLAG([-fwrapv], [CFLAGS="$CFLAGS -fwrapv"])
+])
 
 LIBTOOL_OLD_FLAGS="$LIBTOOL_EXTRA_FLAGS"
 LIBTOOL_EXTRA_FLAGS="$LIBTOOL_EXTRA_FLAGS -version-info $SODIUM_LIBRARY_VERSION"