Linux CentOS 7 setup script

Add a script to set up a Linux CentOS 7 machine so that it can be used
to build the precompiled libraries for Linux.

Reviewed By: sergey, brecht

Differential Revision: https://developer.blender.org/D16171

build_files/build_environment/linux/linux-centos7-setup.sh

@@ -0,0 +1,65 @@
+#!/bin/sh
+
+set -e
+
+if [ `id -u` -ne 0 ]; then
+   echo "This script must be run as root"
+   exit 1
+fi
+
+# yum-config-manager does not come in the default minimal install,
+# so make sure it is installed and available.
+yum -y update
+yum -y install yum-utils
+
+# Install all the packages needed for a new toolchain.
+#
+# NOTE: Keep this separate from the packages install, since otherwise
+# older toolchain will be installed.
+yum -y update
+yum -y install epel-release
+yum -y install centos-release-scl
+yum -y install devtoolset-9
+
+# Install packages needed for Blender's dependencies.
+yum -y install -y  \
+    git subversion bzip2 tar cmake3 patch make autoconf automake libtool  \
+    meson ninja-build \
+    libXrandr-devel libXinerama-devel libXcursor-devel libXi-devel  \
+    libX11-devel libXt-devel  \
+    mesa-libEGL-devel mesa-libGL-devel mesa-libGLU-devel \
+    zlib-devel  \
+    rubygem-asciidoctor \
+    wget tcl yasm python36 python-setuptools bison flex \
+    ncurses-devel \
+    wayland-devel libwayland-client libwayland-server \
+
+
+# Dependencies for Mesa
+yum -y install expat-devel
+python3 -m pip install mako
+
+# Dependencies for pip (needed for buildbot-worker).
+yum -y install python36-pip python36-devel
+
+# Dependencies for asound.
+yum -y install -y  \
+    alsa-lib-devel pulseaudio-libs-devel
+
+alternatives --install /usr/local/bin/cmake cmake /usr/bin/cmake 10  \
+    --slave /usr/local/bin/ctest ctest /usr/bin/ctest  \
+    --slave /usr/local/bin/cpack cpack /usr/bin/cpack  \
+    --slave /usr/local/bin/ccmake ccmake /usr/bin/ccmake  \
+    --family cmake
+
+alternatives --install /usr/local/bin/cmake cmake /usr/bin/cmake3 20  \
+    --slave /usr/local/bin/ctest ctest /usr/bin/ctest3  \
+    --slave /usr/local/bin/cpack cpack /usr/bin/cpack3  \
+    --slave /usr/local/bin/ccmake ccmake /usr/bin/ccmake3  \
+    --family cmake
+
+alternatives --install /usr/local/bin/cmake cmake /usr/bin/cmake3 20  \
+    --slave /usr/local/bin/ctest ctest /usr/bin/ctest3  \
+    --slave /usr/local/bin/cpack cpack /usr/bin/cpack3  \
+    --slave /usr/local/bin/ccmake ccmake /usr/bin/ccmake3  \
+    --family cmake