FYI: when build and src are the same directory, there is no error message. However, when src and build are in seperate directories (e.g.,

build = '.',
src = '../src/python-2.7.11'

the following message occurs MANY times:

unable to execute '../src/python-2.7.11/Modules/ld_so_aix': No such file or directory

during configure the file
./Modules/ld_so_aix is 'created' in the build area.

root@x064:[/data/prj/aixtools/python-2.7.11]ls -l Modules/ld*aix*
-rwxr-xr-x   1 root     system         6205 Mar 02 16:24 Modules/ld_so_aix

Just guessing, but a line such as:
BLDSHARED="\$(srcdir)/Modules/ld_so_aix \$(CC) -bI:\$(srcdir)/Modules/python.exp"

using $(srcdir) is not correct.

Further, a find in $(srcdir) for ld_so_aix returns:
root@x064:[/data/prj/aixtools/python-2.7.11]ls -dl ../src/py*
drwxr-xr-x  17 199      1954           4096 May 23 2015  ../src/python-2.7.10
drwxr-xr-x  17 199      1954           4096 Dec 05 19:47 ../src/python-2.7.11

So, $(srcdir) seems to be wrong, by definition.

For now, I am copying $(srcdir) to $(builddir) to work-around this.