tests/docker: Install gcrypt devel package in Debian image

tests/docker: Install gcrypt devel package in Debian image

In commit 6f8bbb374be we enabled building with the gcrypt library
on the the Debian 'x86 host', which was based on Debian Stretch.
Later in commit 698a71edbed we upgraded the Debian base image to
Buster.

Apparently Debian Stretch was listing gcrypt as a QEMU dependency,
but this is not the case anymore in Buster, so we need to install
it manually (it it not listed by 'apt-get -s build-dep qemu' in
the common debian10.docker anymore). This fixes:

 $ ../configure $QEMU_CONFIGURE_OPTS

  ERROR: User requested feature gcrypt
         configure was not able to find it.
         Install gcrypt devel >= 1.5.0

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200322120104.21267-3-philmd@redhat.com>
Message-Id: <20200323161514.23952-9-alex.bennee@linaro.org>