re: msg286115, 

1) Building modules in the tree during the build process.
** if "in the tree" means building outside of source - such as:
../src/python-X.Y.Z/configure ...
make

** the tarball for Python-2.7.13 is building from ../src/Python-2.7.13/configure where as ../src/Python-2.7.12/configure and the earlier (ones I tried) were not.

** However, 'make distclean' is not working. 
   Further details in a later issue - this bit about make distclean id merely FYI. 

2) In-tree testing of build module feature (test_distutils).

** Is this as simple as (from the 'build directory':
make test 

** shall check this later, make test in general seems to be working - is test_distutils a specific test you want verified?
3) Building and installing modules with an installed version of Python.
** FYI: this will work with the 5 lines deleted - as I mentioned above.
   This is how I manually patched _sysconfigdata.py in Python-2.7.12 when I ran into this.

Now reading the other comments from last night...

re: 286172 and 286173

Short response:
it looks as if patches elsewhere in the 'auto' config files has taken care of this issue - at least for Python-2.7

I shall download and check the latest Python-3.{4|5|6} and report back.