[glibmm] Meson/MSVC: Add more warnings to ignore

[Chun-wei Fan <fanchunwei src gnome org>]

commit fb915e41b9ba2fee52b9b85384a0061a75ba3bdd
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon May 23 15:39:37 2022 +0800

    Meson/MSVC: Add more warnings to ignore
    
    We can actually silence more warnings here, since the issues that they cover
    can normally be fished out by the unit tests.

 meson.build | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/meson.build b/meson.build
index cf632f0c..46b72be0 100644
--- a/meson.build
+++ b/meson.build
@@ -238,6 +238,9 @@ if is_msvc
                                      # dangerous ones glaring, distributed with GLib
     '/EHsc',  # avoid warnings caused by exception handling model used
     '/utf-8', # Avoid C4819 unicode conversion warnings when building on CJK locales
+    '/wd4589', # Constructor of abstract class 'bb' ignores
+               # initializer for virtual base class 'aa'
+    '/wd4702', # unreachable code
   ]
   if host_machine.cpu_family() == 'x86_64' or host_machine.cpu_family() == 'aarch64'
   # 'var' : conversion from 'size_t' to 'type', possible loss of data (applies on 64-bit builds)