`update_file_lists.sh` depends on Bash features, thus needs Bash sebang.
I noticed that running this script as `./update_file_lists.sh` on MacOS
was corrupting `cmake/extract_includes.bat.in`. Forcing the shell to
Bash fixes the generated file output.
diff --git a/update_file_lists.sh b/update_file_lists.sh
index 9c0fbdc..1529199 100755
--- a/update_file_lists.sh
+++ b/update_file_lists.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
# This script copies source file lists from src/Makefile.am to cmake files.
