[gtk/backports-for-4-4: 14/19] compose: Document how to get compose-parse input from libX11 source

[Matthias Clasen <matthiasc src gnome org>]

commit 252b1653e308c1139437a1292b6085a62c84e795
Author: Simon McVittie <smcv debian org>
Date:   Mon Aug 30 10:48:49 2021 +0100

    compose: Document how to get compose-parse input from libX11 source
    
    Signed-off-by: Simon McVittie <smcv debian org>

 gtk/compose/compose-parse.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gtk/compose/compose-parse.c b/gtk/compose/compose-parse.c
index a1ec09d00d..385a34fb77 100644
--- a/gtk/compose/compose-parse.c
+++ b/gtk/compose/compose-parse.c
@@ -7,6 +7,7 @@
  * character data, and definitions for the builtin compose table of GTK.
  * Run it like this:
  *
+ *   cpp -DXCOMM='#' Compose.pre | sed -e 's/^ *#/#/' > Compose
  *   compose-parse Compose sequences-little-endian sequences-big-endian chars gtkcomposedata.h
  *
  * The GTK build expects the output files to be in the source tree, in