Trac #28883: update pkgconfig to version 1.5.1

the current version is buggy, as we found out on #27870

also, pkgconfig switched to https://python-poetry.org/ from setuptools,
so we either get poetry installed too (which is a big task), or go
Debian way and provide `setup.py`. That's what they do in their (not
really "orig") tarball on

http://deb.debian.org/debian/pool/main/p/python-pkgconfig/

Cf. https://salsa.debian.org/python-team/modules/python-
pkgconfig/tree/master

The pypi tarball has setup.py, so we can just use it.
tarball: https://files.pythonhosted.org/packages/6e/a9/ff67ef67217dfdf2a
ca847685fe789f82b931a6957a3deac861297585db6/pkgconfig-1.5.1.tar.gz

URL: https://trac.sagemath.org/28883
Reported by: dimpase
Ticket author(s): Dima Pasechnik
Reviewer(s): Isuru Fernando, Erik Bray, Matthias Koeppe

build/pkgs/pkgconfig/checksums.ini

@@ -1,4 +1,4 @@
 tarball=pkgconfig-VERSION.tar.gz
-sha1=d412ffa23fb016affc0b4d2a0ed656f34d960812
-md5=f3a5314d7364832b26f404eae4722bbb
-cksum=261359121
+sha1=1e844638e8ba3886b6a28b86500c4414ba910b4e
+md5=9f9cdb224ec0a1e59efcc7cac4b91972
+cksum=1169273382

build/pkgs/pkgconfig/package-version.txt

@@ -1 +1 @@
-1.4.0
+1.5.1

src/module_list.py

@@ -39,7 +39,11 @@
 png_include_dirs = png_pc['include_dirs']
 
 # zlib
-zlib_pc = pkgconfig.parse('zlib')
+try:
+    zlib_pc = pkgconfig.parse('zlib')
+except pkgconfig.PackageNotFoundError:
+    from collections import defaultdict
+    zlib_pc = defaultdict(list, {'libraries': ['z']})
 zlib_libs = zlib_pc['libraries']
 zlib_library_dirs = zlib_pc['library_dirs']
 zlib_include_dirs = zlib_pc['include_dirs']