win: add new win-pkgconfig subproject

This subprojects provides the pkg-config.exe binary on Windows
required by g-ir-scanner to build introspection GIR's

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1584>

meson.build

@@ -116,6 +116,7 @@ if get_option('build-tools-source') == 'subproject'
   if build_system == 'windows'
     subproject('win-flex-bison-binaries')
     subproject('win-nasm')
+    subproject('win-pkgconfig')
   elif build_system == 'darwin'
     subproject('macos-bison-binary')
     # Newer macOS provides /usr/lib/pkgconfig/libpcre2-8.pc which is broken

subprojects/win-pkgconfig/download-binary.py

@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import ssl
+import zipfile
+import hashlib
+import urllib.request
+import urllib.error
+
+# Disable certificate checking because it always fails on Windows
+# We verify the checksum anyway.
+ctx = ssl.create_default_context()
+ctx.check_hostname = False
+ctx.verify_mode = ssl.CERT_NONE
+
+BASENAME = 'pkg-config.zip'
+GSTREAMER_URL = 'https://gstreamer.freedesktop.org/src/mirror/pkg-config.zip'
+
+zip_sha256 = sys.argv[1]
+source_dir = os.path.join(
+    os.environ['MESON_SOURCE_ROOT'], os.environ['MESON_SUBDIR'])
+dest = BASENAME
+dest_path = os.path.join(source_dir, dest)
+
+
+def get_sha256(zipf):
+    hasher = hashlib.sha256()
+    with open(zipf, 'rb') as f:
+        hasher.update(f.read())
+    return hasher.hexdigest()
+
+
+if os.path.isfile(dest_path):
+    found_sha256 = get_sha256(dest_path)
+    if found_sha256 == zip_sha256:
+        print('{} already downloaded'.format(dest))
+        sys.exit(0)
+    else:
+        print('{} checksum mismatch, redownloading'.format(dest))
+
+url = GSTREAMER_URL.format(dest)
+print('Downloading {} to {}'.format(GSTREAMER_URL.format(dest), dest))
+try:
+    with open(dest_path, 'wb') as d:
+        f = urllib.request.urlopen(url, context=ctx)
+        d.write(f.read())
+except urllib.error.URLError as ex:
+    curdir = os.path.dirname(sys.argv[0])
+    print('Couldn\'t download {!r}! Try downloading it manually and '
+          'placing it into {!r}'.format(dest, curdir))
+
+found_sha256 = get_sha256(dest_path)
+if found_sha256 != zip_sha256:
+    print('SHA256 of downloaded file {} was {} instead of {}'
+          ''.format(dest, found_sha256, zip_sha256))
+    sys.exit(1)
+
+print('Extracting {}'.format(dest))
+zf = zipfile.ZipFile(dest_path, "r")
+zf.extractall(path=source_dir)

subprojects/win-pkgconfig/meson.build

@@ -0,0 +1,19 @@
+project('win-pkgconfig', version : '0.29.2')
+
+py3 = import('python3').find_python()
+
+if host_machine.system() != 'windows'
+  error('Can only download pkgconfig for Windows, sorry')
+endif
+
+message('Downloading pkg-config.exe binary for Windows...')
+
+zip_hash = 'b74be141a53f193727fdcb33e9a052a38d9b79c6262326d264e502796b73dfe1'
+
+ret = run_command(py3, files('download-binary.py'), zip_hash, check: true)
+if ret.returncode() != 0
+  message(ret.stdout())
+  error(ret.stderr())
+endif
+
+meson.override_find_program('pkg-config', find_program('pkg-config.exe'))