Mofification needed to build lcgmake on Centos8

• More packages are taken from the system for centos8: uuid libxml2 zlib expat bzip2 xz curl motif libaio lz4 jpeg gmp libedit libevent autoconf automake m4
• Do not build pygsi for centos8 (not supported, old, not needed by anyone)
• Do not build CORAL and COOL for centos8
• Do not build catboost for centos8 (catboost used (still?) by LHCb)
• Upgrade Doxygen to 1.8.18
• Downgrade flex to 2.6.3 for centos8 only (Flex 2.6.4 segfaults during build, see https://github.com/westes/flex/issues/219. To be fixed in 2.6.5)
• Add missing zlib dependency to png
• Add libtool dependency to jpeg, also add --build-shared build flag
• Pass a path to expat for fontconfig explicitly (was working as we always had system expat)
• Add -no-feature-renameat2 -no-feature-getentropy options to Qt5 to avoid failures using centos8 image on systems with older kernels.
• Take m4, autoconf, automake for Centos8 from system
• Add patch for zstandard to respect CC env variable
• Don't build CORAL and COOL for Centos8, rpc.h is provided by different package in Centos8
• glib is not available in centos8 repo, build it from sources for centos8
• Use hadoop 3XX for centos8 due to incomptible system openssl
• Add patch to use rpc from libtirpc-devel.x86_64 needed by hadoop hadoop-pipes
• Add patch to grpcio to work without system cc
• Add libaio dependency to oracle
• Use centos7 binaries of grid packages for centos8
• Add missing dependency swig to m2crypto
• Use go from centos7 to build go
• Add patch for m4 to deal with glibc 2.28
• Add flex to motif deps.
• Reduce powheg-box2 build time building all processes in parallel. (Refuction from 3-40h to 1-40h)
• Update libxml2 to 2.9.10, lxml to 4.6.2 and libxslt to 1.1.34, add cython dependency to lxml and regenerate C file with it, fixes import etree from lxml for Ubuntu20