I found cause of my problem with building libc6-dev package on Jessie.
Code is invoked in following, simplified order
1. $ git buildpackage 2. code compilation 3. pbuilder invocation 4. package building in pbuilder environment
It should be obvious, but neither I noticed nor I thought that it is done that way.
Currently I’m examining if it will be possible to change order of steps to:
1. $ git buildpackage 2. pbuilder invocation 3. code compilation in pbuilder environment 4. package building in pbuilder environment