Build failure with clang

[jserv]

While building xv6 with clang, tools/sign.pl complains:

$ make CC=clang
...
boot block too large: 894 bytes (max 510)
Makefile:119: recipe for target 'out/bootblock' failed

The version of clang:
$ clang --version
Ubuntu clang version 3.6.0-2ubuntu1 (tags/RELEASE_360/final) (based on LLVM 3.6.0)

[alsmoreira]

please use GCC 4.4 instead of GCC 4.6+ to produce smaller files within boot block limit. GCC 4.4 is available in Debian 7.0 (stable). Or in line 40, change O2 to Os

[lynnt]

I tried to use GCC 4.4 along Os but it still results into the same result. Do you have any other suggestions by any chance?