ci/linux32: libify install-dependencies step

In a later patch, we will add new Travis Job for linux-musl.
Most of other code in this file could be reuse for that job.

Move the code to install dependencies to a common script.
Should we add new CI system that can run directly in container,
we can reuse this script for installation step.

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ci/install-docker-dependencies.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+#
+# Install dependencies required to build and test Git inside container
+#
+
+case "$jobname" in
+Linux32)
+	linux32 --32bit i386 sh -c '
+		apt update >/dev/null &&
+		apt install -y build-essential libcurl4-openssl-dev \
+			libssl-dev libexpat-dev gettext python >/dev/null
+	'
+	;;
+esac