I have edited the registry key
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\MSBuild\ToolsVersions\12.0\11.0
and
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSBuild\ToolsVersions\12.0\11.0
to use the V120 directory
Now my server build the solution, but i don't understand why MSBuild use the key
ToolsVersions\12.0\11.0
and not the key ToolsVersions\12.0\12.0
Parhaps it's due to the v120_xp platform toolset