meson.build: print a summary of the DDX to build

Makes it easier to detect accidentally "oops, i'm not building Xwayland"

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1869>

hw/meson.build

@@ -1,8 +1,8 @@
-if get_option('xephyr')
+if build_xephyr
     subdir('kdrive')
 endif
 
-if get_option('xvfb')
+if build_xvfb
     subdir('vfb')
 endif
 

meson.build

@@ -287,6 +287,21 @@ if build_xquartz
     build_rootless = true
 endif
 
+build_xephyr = get_option('xephyr')
+build_xvfb = get_option('xvfb')
+
+summary({
+        'Xorg': build_xorg,
+        'Xwayland': build_xwayland,
+        'Xnest': build_xnest,
+        'Xvfb': build_xvfb,
+        'Xwin': build_xwin,
+        'Xquartz': build_xquartz,
+    },
+    section: 'DDX',
+    bool_yn: true,
+)
+
 # IPv6 support
 have_AF_INET6 = cc.compiles('''
 #ifdef WIN32