build system incorrectly handles CC, CFLAGS, LDFLAGS, and related.

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-05-12.17:00:57.839>
labels = ['build']
title = 'build system incorrectly handles CC, CFLAGS, LDFLAGS, and related.'
updated_at = <Date 2018-05-16.05:10:02.297>
user = 'https://github.com/grimreaper'

bugs.python.org fields:

activity = <Date 2018-05-16.05:10:02.297>
actor = 'eitan.adler'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Build']
creation = <Date 2018-05-12.17:00:57.839>
creator = 'eitan.adler'
dependencies = []
files = []
hgrepos = []
issue_num = 33473
keywords = ['patch']
message_count = 1.0
messages = ['316431']
nosy_count = 1.0
nosy_names = ['eitan.adler']
pr_nums = ['6771', '6890']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue33473'
versions = []