Easy Fix, o que você precisa fazer é especificar a versão do libc6-dev que você deseja instalar (o openvz, neste caso), e ele será instalado corretamente.
Heres como descobrir o que você quer, ok, digamos que você vai fazer
apt-get install libc6-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
libc6-dev : Depends: libc6 (= 2.15-0ubuntu10.4) but 2.15-0ubuntu10+openvz0 is to be installed
Recommends: gcc but it is not going to be installed or
c-compiler
E: Unable to correct problems, you have held broken packages.
Neste caso, você quer instalar a versão 2.15-0ubuntu10 + openvz0, tente novamente especificando a versão como esta (observe a versão = no final da linha agora):
apt-get install libc6-dev=2.15-0ubuntu10+openvz0
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
libc6-dev : Depends: libc-dev-bin (= 2.15-0ubuntu10+openvz0)
Recommends: gcc but it is not going to be installed or
c-compiler
E: Unable to correct problems, you have held broken packages.
Como você pode ver aqui, acabou sendo mais um pacote que queria uma versão 'openvz', então eu adicionei esse pacote na linha de instalação do apt-get novamente, especificando a versão
apt-get install libc6-dev=2.15-0ubuntu10+openvz0 libc-dev-bin=2.15-0ubuntu10+openvz0
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
gcc gcc-4.6 libquadmath0 linux-libc-dev manpages-dev
Suggested packages:
gcc-multilib autoconf automake1.9 libtool flex bison gdb gcc-doc gcc-4.6-multilib libmudflap0-4.6-dev gcc-4.6-doc gcc-4.6-locales libgcc1-dbg
libgomp1-dbg libquadmath0-dbg libmudflap0-dbg binutils-gold glibc-doc
The following NEW packages will be installed:
gcc gcc-4.6 libc-dev-bin libc6-dev libquadmath0 linux-libc-dev manpages-dev
0 upgraded, 7 newly installed, 0 to remove and 4 not upgraded.
Need to get 13.6 MB of archives.
After this operation, 33.5 MB of additional disk space will be used.
Do you want to continue [Y/n]?
E agora funciona !!!
Espero que isso tenha ajudado você, eu corri para mim mesmo algumas vezes e sabendo como consertá-lo CORRETAMENTE pode ajudar muito, existem maneiras alternativas de contornar o erro, mas este é o 'correto 'caminho.