I failed to follow through the logic of the makefile, or work out why this is different on debian jessie, but this ended up generating a dependency on the directory including a trailing slash, but the generated build rule to mkdir the directory is being generated with the trailing slash stripped on line 113.
I failed to follow through the logic of the makefile, or work out why this is different on debian jessie, but this ended up generating a dependency on the directory including a trailing slash, but the generated build rule to mkdir the directory is being generated with the trailing slash stripped on line 113.