build: Do not install anything in xsessions when X11 is disabled

Fixes: b05eb4eb6d ("build: Allow disabling the X11 session")
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/400>
(cherry picked from commit 2552c92fe1)

data/meson.build

@@ -26,7 +26,7 @@ foreach name : session_desktops
     #        There is a workaround in meson/session-post-install.py until proper
     #        solution arises:
     #        https://github.com/mesonbuild/meson/issues/2416
-    session_instdir = xsessiondir
+    session_instdir = wlsessiondir
   #session_instdir = [ xesssiondir, wlsessiondir ]
   endif
   i18n.merge_file(

meson.build

@@ -31,6 +31,8 @@ shell_version = ver_arr[0]
 
 uuid_suffix = '@gnome-shell-extensions.gcampax.github.com'
 
+have_x11 = get_option('x11')
+
 classic_extensions = [
   'apps-menu',
   'places-menu',
@@ -86,10 +88,12 @@ endforeach
 
 if classic_mode_enabled
   subdir('data')
-  meson.add_install_script(
-    'meson/session-post-install.py',
-    join_paths(get_option('prefix'), datadir),
-  )
+  if have_x11
+    meson.add_install_script(
+      'meson/session-post-install.py',
+      join_paths(get_option('prefix'), datadir),
+    )
+  endif
 endif
 
 subdir('extensions')

meson/session-post-install.py

@@ -15,10 +15,10 @@ else:
 
 # FIXME: Meson is unable to copy a generated target file:
 #        https://groups.google.com/forum/#!topic/mesonbuild/3iIoYPrN4P0
-dst_dir = os.path.join(install_root, 'wayland-sessions')
+dst_dir = os.path.join(install_root, 'xsessions')
 if not os.path.exists(dst_dir):
   os.makedirs(dst_dir)
 
-src = os.path.join(install_root, 'xsessions', 'gnome-classic.desktop')
+src = os.path.join(install_root, 'wayland-sessions', 'gnome-classic.desktop')
 dst = os.path.join(dst_dir, 'gnome-classic.desktop')
 shutil.copyfile(src, dst)