meson: bump submodule to 0.59.3

This gains some bugfixes, especially:

- it fixes the introspection of array options.  While technically we
still support Meson 0.58.2, this issue only appears when adding a new
option and not if the user is just building QEMU.  In the relatively
rare case of a contributor using --meson to point to a 0.58 version,
review can catch spurious changes to scripts/meson-buildoptions.sh
easily.

- it fixes "meson test" when it is not the process group leader.  Make is
the process group leader when "make check" invokes "meson test", so this
is a requirement for using it as a test harness.

Tested-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/meson-buildoptions.py

@@ -150,23 +150,7 @@ def print_parse(options):
     print("}")
 
 
-def fixup_options(options):
-    # Meson <= 0.60 does not include the choices in array options, fix that up
-    for opt in options:
-        if opt["name"] == "trace_backends":
-            opt["choices"] = [
-                "dtrace",
-                "ftrace",
-                "log",
-                "nop",
-                "simple",
-                "syslog",
-                "ust",
-            ]
-
-
 options = load_options(json.load(sys.stdin))
-fixup_options(options)
 print("# This file is generated by meson-buildoptions.py, do not edit!")
 print_help(options)
 print_parse(options)