main: Make process PR_SET_DUMPABLE

Otherwise we won't get core dumps if the launching binary has
capabilities set.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/811

config.h.meson

@@ -61,6 +61,9 @@
 /* XKB base prefix */
 #mesondefine XKB_BASE
 
+/* Whether <sys/prctl.h> exists and it defines prctl() */
+#mesondefine HAVE_SYS_PRCTL
+
 /* Either <sys/random.h> or <linux/random.h> */
 #mesondefine HAVE_SYS_RANDOM
 #mesondefine HAVE_LINUX_RANDOM

meson.build

@@ -366,6 +366,10 @@ cdata.set('HAVE_PROFILER', have_profiler)
 xkb_base = xkeyboard_config_dep.get_pkgconfig_variable('xkb_base')
 cdata.set_quoted('XKB_BASE', xkb_base)
 
+if cc.has_header_symbol('sys/prctl.h', 'prctl')
+  cdata.set('HAVE_SYS_PRCTL', 1)
+endif
+
 if have_wayland
   xwayland_path = get_option('xwayland_path')
   if xwayland_path == ''

src/core/main.c

@@ -70,6 +70,10 @@
 #include <systemd/sd-login.h>
 #endif /* HAVE_WAYLAND && HAVE_NATIVE_BACKEND */
 
+#ifdef HAVE_SYS_PRCTL
+#include <sys/prctl.h>
+#endif
+
 #include "backends/meta-backend-private.h"
 #include "backends/x11/cm/meta-backend-x11-cm.h"
 #include "backends/x11/meta-backend-x11.h"
@@ -532,6 +536,10 @@ meta_init (void)
   MetaCompositorType compositor_type;
   GType backend_gtype;
 
+#ifdef HAVE_SYS_PRCTL
+  prctl (PR_SET_DUMPABLE, 1);
+#endif
+
   sigemptyset (&empty_mask);
   act.sa_handler = SIG_IGN;
   act.sa_mask    = empty_mask;