[gimp] meson: missing test for sys/prctl.h.

[Jehan <jehanp src gnome org>]

commit 44f6ee36fe970d31a8eaf6ebbfc3d745dfd149cc
Author: Jehan <jehan girinstud io>
Date:   Sat Dec 4 18:49:00 2021 +0100

    meson: missing test for sys/prctl.h.
    
    This is needed for prctl(), to allow a child process to trace the
    parent.

 meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/meson.build b/meson.build
index f7b7436663..cb4bb5d8c7 100644
--- a/meson.build
+++ b/meson.build
@@ -1246,6 +1246,7 @@ foreach header : [
     { 'm': 'HAVE_STRING_H',       'v': 'string.h' },
     { 'm': 'HAVE_STRINGS_H',      'v': 'strings.h' },
     { 'm': 'HAVE_SYS_PARAM_H',    'v': 'sys/param.h' },
+    { 'm': 'HAVE_SYS_PRCTL_H',    'v': 'sys/prctl.h' },
     { 'm': 'HAVE_SYS_SELECT_H',   'v': 'sys/select.h' },
     { 'm': 'HAVE_SYS_STAT_H',     'v': 'sys/stat.h' },
     { 'm': 'HAVE_SYS_THR_H',      'v': 'sys/thr.h' },