Error Compiling Xen-unstable Changeset 26004

["Singapore Citizen Mr. Teo En Ming (Zhang Enming)" <singapore.mr.teo.en.ming@gmail.com>]

Dear Ian and Konrad,

I encountered an error when compiling Xen-unstable changeset 26004.

The error is reproduced as follows:

/usr/bin/ld: vl.o: undefined reference to symbol 
'timer_settime@@GLIBC_2.3.3'
/usr/bin/ld: note: 'timer_settime@@GLIBC_2.3.3' is defined in DSO 
/lib/x86_64-linux-gnu/librt.so.1 so try adding it to the linker command line
/lib/x86_64-linux-gnu/librt.so.1: could not read symbols: Invalid operation
collect2: error: ld returned 1 exit status
make[5]: *** [qemu-dm] Error 1
make[5]: Leaving directory 
`/home/teo-en-ming/xen-unstable.hg-cs26004-vga-passthrough/tools/qemu-xen-traditional-dir-remote/i386-dm'
make[4]: *** [subdir-i386-dm] Error 2
make[4]: Leaving directory 
`/home/teo-en-ming/xen-unstable.hg-cs26004-vga-passthrough/tools/qemu-xen-traditional-dir-remote'
make[3]: *** [subdir-install-qemu-xen-traditional-dir] Error 2
make[3]: Leaving directory 
`/home/teo-en-ming/xen-unstable.hg-cs26004-vga-passthrough/tools'
make[2]: *** [subdirs-install] Error 2
make[2]: Leaving directory 
`/home/teo-en-ming/xen-unstable.hg-cs26004-vga-passthrough/tools'
make[1]: *** [install-tools] Error 2
make[1]: Leaving directory 
`/home/teo-en-ming/xen-unstable.hg-cs26004-vga-passthrough'
make: *** [world] Error 2

How do I solve this problem?

Thank you very much.

-- 
Yours sincerely,

Singapore Citizen Mr. Teo En Ming (Zhang Enming)