common: support disabling python shebang rewriting

useful if there are special python-containing shebangs that should not
be rewritten, for example with Ghidra's embedded jython.

common/hooks/post-install/04-create-xbps-metadata-scripts.sh

@@ -272,7 +272,7 @@ _EOF
 		fi
 	fi
 
-	if [ -n "$python_version" ]; then
+	if [ -n "$python_version" ] && [ "$python_version" != ignore ]; then
 		pycompile_version=${python_version}
 	fi