According to https://bitcointalk.org/index.php?topic=495683.msg5471918#msg5471918, the resulting executables from gitian no longer work on debian 7.4 (stable).

bitcoind: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.15' not found (required by bitcoind)
bitcoind: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.14' not found (required by bitcoind)

This is caused by switching the gitian build to VMs using Ubuntu 12.04 (which uses GLIBC_2.15).

I investigated and the only symbol that we actually use from GLIBC_2.14/15 is:

$ objdump -T bitcoin-0.9.0rc2-linux/bin/32/bitcoin-qt |grep GLIBC_2.15
00000000      DF *UND*  00000000  GLIBC_2.15  __fdelt_chk

__fdelt_chk is part of the FORTIFY_SOURCE functionality and was indeed introduced in glibc 2.15.

We may be able to remove dependency on this symbol by undefining FORTIFY_SOURCE, but as it is part of a hardening feature I'm not really happy about that.