scons: set HAVE_FUNC_ATTRIBUTE_ALIAS

Analogoust to the previous commit were we did so for autotools

Cc: Jose Fonseca <jfonseca@vmware.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
diff --git a/include/c99_compat.h b/include/c99_compat.h
index 24e96e0..cb690c6 100644
--- a/include/c99_compat.h
+++ b/include/c99_compat.h
@@ -163,6 +163,7 @@
 #    define HAVE_FUNC_ATTRIBUTE_UNUSED 1
 #    define HAVE_FUNC_ATTRIBUTE_FORMAT 1
 #    define HAVE_FUNC_ATTRIBUTE_PACKED 1
+#    define HAVE_FUNC_ATTRIBUTE_ALIAS 1
 
 #    if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
        /* https://gcc.gnu.org/onlinedocs/gcc-4.3.6/gcc/Other-Builtins.html */