[calls] meson: Build manpage with rst2man

[Evangelos Ribeiro Tzaras <devrtz src gnome org>]

commit 6738962073008e2067e11be3082c19048d46a0cb
Author: Evangelos Ribeiro Tzaras <devrtz fortysixandtwo eu>
Date:   Tue May 31 20:03:49 2022 +0200

    meson: Build manpage with rst2man
    
    Closes #457

 doc/meson.build   | 16 ++++++++++++++++
 meson_options.txt |  4 ++++
 2 files changed, 20 insertions(+)
---
diff --git a/doc/meson.build b/doc/meson.build
index d7d728a6..39d6e8f5 100644
--- a/doc/meson.build
+++ b/doc/meson.build
@@ -44,3 +44,19 @@ gnome.gtkdoc('calls',
             install: true)
 
 endif
+
+rst2man = find_program('rst2man', 'rst2man.py', required: false)
+if get_option('manpages') and not rst2man.found()
+   error('No rst2man found, but man pages were explicitly enabled')
+endif
+
+if get_option('manpages') and rst2man.found()
+  custom_target('man-gnome-calls',
+    input: 'gnome-calls.rst',
+    output: 'gnome-calls.1',
+    command: [rst2man, '@INPUT@'],
+    capture: true,
+    install: true,
+    install_dir: get_option('mandir') / 'man1',
+  )
+endif
diff --git a/meson_options.txt b/meson_options.txt
index 41f2046e..141ed300 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -5,3 +5,7 @@ option('gtk_doc',
 option('tests',
        type: 'boolean', value: true,
        description: 'Whether to compile unit tests')
+
+option('manpages',
+       type: 'boolean', value: true,
+       description: 'Whether to generate man pages')