idna: fix build due to missing setup.py.

Looks like PyPi tarball doesn't have setup.py, which jhbuild needs:

2024-02-06T16:42:10.5816920Z *** Building python3-idna *** [90/137]
2024-02-06T16:42:10.5822330Z python3 setup.py build --build-base /Users/runner/.cache/jhbuild/build/idna-3.6
2024-02-06T16:42:10.7839920Z python3: can't open file '/Users/runner/gtk/source/idna-3.6/setup.py': [Errno 2] No such file or directory
2024-02-06T16:42:10.8055060Z *** Error during phase build of python3-idna: ########## Error running python3 setup.py build --build-base /Users/runner/.cache/jhbuild/build/idna-3.6 *** [90/137]

https://github.com/cpatulea/gtk-osx-build/actions/runs/7802110330/job/21278777736

Add it back using a patch.

Xpra-org/xpra#4017 (comment)

patches/idna-setup-py.patch

@@ -0,0 +1,16 @@
+commit 61401d62c557246600b45d09d471450e97b8c6f0
+Author: Catalin Patulea <[email protected]>
+Date:   Sat Jan 27 11:32:52 2024 +0000
+
+    Add skeleton setup.py.
+
+diff --git a/setup.py b/setup.py
+new file mode 100755
+index 0000000..851cb3f
+--- /dev/null
++++ b/setup.py
+@@ -0,0 +1,3 @@
++#!/usr/bin/env python3
++from setuptools import setup
++setup()
+\ No newline at end of file

xpra-python3.modules

@@ -790,7 +790,9 @@
 		<branch
 			module="i/idna/idna-3.6.tar.gz"
 			hash="sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca"
-			version="3.6"/>
+			version="3.6">
+			<patch file="idna-setup-py.patch" strip="1"/>
+		</branch>
 		<dependencies>
 			<dep package="python3"/>
 		</dependencies>