pkg-config file misses flags for static linking

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-05-07.10:55:52.293>
labels = ['3.8', 'type-bug', '3.7', 'build']
title = 'pkg-config file misses flags for static linking'
updated_at = <Date 2018-05-07.12:14:11.893>
user = 'https://github.com/pitrou'

bugs.python.org fields:

activity = <Date 2018-05-07.12:14:11.893>
actor = 'pitrou'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Build']
creation = <Date 2018-05-07.10:55:52.293>
creator = 'pitrou'
dependencies = []
files = []
hgrepos = []
issue_num = 33438
keywords = []
message_count = 4.0
messages = ['316258', '316259', '316260', '316263']
nosy_count = 3.0
nosy_names = ['barry', 'doko', 'pitrou']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33438'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']