target/hexagon/idef-parser/prepare: use env to invoke bash

target/hexagon/idef-parser/prepare: use env to invoke bash

This file is the only one involved in the compilation process which
still uses the /bin/bash path.

Signed-off-by: Samuel Tardieu <sam@rfc1149.net>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Message-ID: <20231123211506.636533-1-sam@rfc1149.net>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>