[issue22100] Use $HOSTPYTHON when determining candidate interpreter for $PYTHON_FOR_BUILD.

[Ned Deily]

Changes by Ned Deily <nad at acm.org>:


----------
nosy: +doko
versions:  -Python 3.3

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue22100>
_______________________________________