By default generate-version-script.py uses /usr/bin/python3, whatever
version that may be - which causes problems if the default python3
installation is one either built without XML support or not included
in PYTHON_TARGETS of dev-python/setuptools. Make sure the script is
invoked using the same interpreter as meson itself, as that one is
already guaranteed to provide both 'xml' and 'pkg_resources'.

--- a/libjcat/meson.build
+++ b/libjcat/meson.build
@@ -129,6 +129,11 @@
     install : true,
   )
 
+  # Make sure generate-version-script.py is invoked by the same python as meson,
+  # as that one must already have both XML support and setuptools.
+  python = import('python')
+  python_interpreter = python.find_installation()
+
   # Verify the map file is correct -- note we can't actually use the generated
   # file for two reasons:
   #
@@ -141,6 +146,7 @@
     input: jcat_gir[0],
     output: 'jcat.map',
     command: [
+      python_interpreter,
       join_paths(meson.source_root(), 'contrib', 'generate-version-script.py'),
       'LIBJCAT',
       '@INPUT@',