Specify bash for androidbuildlibs.sh

This script relies on string indexes in parameter expansions, which
aren't suppored by /bin/sh (e.g. dash).

Based on a patch by Roflcopter4:
https://github.com/joncampbell123/dosbox-x/pull/3850

Signed-off-by: Stephen Kitt <steve@sk2.org>

build-scripts/androidbuildlibs.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 # Build the Android libraries without needing a project
 # (AndroidManifest.xml, jni/{Application,Android}.mk, etc.)