Meson: Fix build with msvc
When compiling glib with meson and MSVC I get this build error:
[115/514] Compiling C object glib/glib@@glib-2.0@sha/gslice.c.obj. FAILED: glib/glib@@glib-2.0@sha/gslice.c.obj cl @glib/glib@@glib-2.0@sha/gslice.c.obj.rsp c:\users\xavier claessens\glib\glib\valgrind.h(463): fatal error C1189: #error: Unsupported compiler.
Edited by Xavier Claessens