[gtk-osx] Set the arm64 condition when building for Apple Silicon.

[John Ralls <jralls src gnome org>]

commit a26a581de4f833ebcdd065018b9a3be4d95d579b
Author: John Ralls <jralls ceridwen us>
Date:   Sat Nov 13 09:19:25 2021 -0800

    Set the arm64 condition when building for Apple Silicon.
    
    Needed to set libnettle's stable config correctly.

 jhbuildrc-gtk-osx | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/jhbuildrc-gtk-osx b/jhbuildrc-gtk-osx
index 13e8baca..22935bec 100644
--- a/jhbuildrc-gtk-osx
+++ b/jhbuildrc-gtk-osx
@@ -287,6 +287,7 @@ def setup_sdk(target=_target, sdk_version=None, architectures=[_default_arch]):
         append_autogenargs("openssl", "darwin64-x86_64-cc #")
     elif architectures == ["arm64"]:
         conditions.add('64-bit')
+        conditions.add('arm64')
         append_autogenargs("glib", "ac_cv_c_bigendian=no")
         append_autogenargs("openssl", "darwin64-arm64-cc #") # Not a legal value
     elif len(set(architectures) - {"i386",  "x86_64", 'arm64'}) > 0: