Add a script to install build-time dependencies

The script can be used both for the devcontainer and for the continuous
integration.

.devcontainer/assets/install-build-deps.sh

+#!/bin/sh
+
+yum-config-manager --add-repo https://openresty.org/package/centos/openresty.repo
+
+yum -y install epel-release
+
+yum -y install \
+    gcc-c++ \
+    GeoIP-devel \
+    gd-devel \
+    gettext \
+    ccache \
+    libxslt-devel \
+    lcov \
+    perl-ExtUtils-Embed \
+    perl-Test-Nginx \
+    perl-Digest-SHA \
+    readline-devel \
+    boost-devel \
+    voms-devel \
+    make \
+    patch