build: Fix manpage generation at dist time

The AsciiDoc API only exposes the capabilities of asciidoc, but not
the related a2x tool. Fix generating the manpages by shelling out
to the command line tool instead.

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4320

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1859>

meson/generate-manpages.py

@@ -2,7 +2,7 @@
 
 import os
 from pathlib import PurePath
-from asciidocapi import AsciiDocAPI
+import subprocess
 
 man_pages = [
     'man/gnome-shell.1',
@@ -12,13 +12,12 @@ man_pages = [
 sourceroot = os.environ.get('MESON_SOURCE_ROOT')
 distroot = os.environ.get('MESON_DIST_ROOT')
 
-asciidoc = AsciiDocAPI()
-
 for man_page in man_pages:
     page_path = PurePath(man_page)
     src = PurePath(sourceroot, page_path.with_suffix('.txt'))
     dst = PurePath(distroot, page_path)
     stylesheet = src.with_name('stylesheet.xsl')
 
-    asciidoc.options('--xsl-file', os.fspath(stylesheet))
-    asciidoc.execute(os.fspath(src), outfile=os.fspath(dst))
+    subprocess.call(['a2x', '--xsl-file', os.fspath(stylesheet),
+      '--format', 'manpage', '--destination-dir', os.fspath(dst.parent),
+      os.fspath(src)])