Revert "[build] Fix build when building out of source tree"
Revert "[build] Fix build when building out of source tree"

This reverts commit fbc16c75f97eea84f9fe1d742ee63c9033486786.

It breaks distcheck.

lanoxx/libwnck,Sidnioulz/SandboxLibwnck,lanoxx/libwnck,Sidnioulz/SandboxLibwnck