Remove temp files that the macOS installer builder leaves hanging.

packaging/createpkg.py

diff --git a/packaging/createpkg.py b/packaging/createpkg.py
index 793d4bf..533b3b9 100755
--- a/packaging/createpkg.py
+++ b/packaging/createpkg.py
@@ -105,6 +105,11 @@
         with open(self.distribution_file, 'w') as open_file:
             open_file.write(doc.toprettyxml())
 
+    def remove_tempfiles(self):
+        shutil.rmtree('macpkg')
+        os.unlink('meson-distribution.xml')
+        os.unlink('meson.pkg')
+        os.unlink('meson.spec')
 
 if __name__ == '__main__':
     if not os.path.exists('meson.py'):
@@ -114,3 +119,4 @@
     pg = PkgGenerator()
     pg.build_dist()
     pg.build_package()
+    pg.remove_tempfiles()