qemu: never use bundled Meson

It's better to fail to build if our version of Meson isn't compatible
with QEMU's, so we'll know something is wrong.  Otherwise, we'll get
subtle breakages that only manifest at runtime, which I think might be
what happened in 9e403b19a1 ("qemu: 5.1.0 -> 5.2.0") to necessitate
autoPatchelfHook.

pkgs/applications/virtualization/qemu/default.nix

@@ -178,6 +178,9 @@ stdenv.mkDerivation rec {
     "--enable-guest-agent"
     "--localstatedir=/var"
     "--sysconfdir=/etc"
+    # Always use our Meson, not the bundled version, which doesn't
+    # have our patches and will be subtly broken because of that.
+    "--meson=meson"
   ] ++ lib.optional numaSupport "--enable-numa"
     ++ lib.optional seccompSupport "--enable-seccomp"
     ++ lib.optional smartcardSupport "--enable-smartcard"